<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!DOCTYPE article PUBLIC "-//NLM//DTD Journal Publishing DTD v2.3 20070202//EN" "journalpublishing.dtd">
<article xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" article-type="research-article">
<front>
<journal-meta>
<journal-id journal-id-type="publisher-id">Front. Earth Sci.</journal-id>
<journal-title>Frontiers in Earth Science</journal-title>
<abbrev-journal-title abbrev-type="pubmed">Front. Earth Sci.</abbrev-journal-title>
<issn pub-type="epub">2296-6463</issn>
<publisher>
<publisher-name>Frontiers Media S.A.</publisher-name>
</publisher>
</journal-meta>
<article-meta>
<article-id pub-id-type="doi">10.3389/feart.2021.630493</article-id>
<article-categories>
<subj-group subj-group-type="heading">
<subject>Earth Science</subject>
<subj-group>
<subject>Original Research</subject>
</subj-group>
</subj-group>
</article-categories>
<title-group>
<article-title>Permafrost Carbon and CO<sub>2</sub> Pathways Differ at Contrasting Coastal Erosion Sites in the Canadian Arctic</article-title>
</title-group>
<contrib-group>
<contrib contrib-type="author" corresp="yes">
<name><surname>Tanski</surname> <given-names>George</given-names></name>
<xref ref-type="aff" rid="aff1"><sup>1</sup></xref>
<xref ref-type="aff" rid="aff2"><sup>2</sup></xref>
<xref ref-type="aff" rid="aff3"><sup>3</sup></xref>
<xref ref-type="corresp" rid="c001"><sup>&#x002A;</sup></xref>
<uri xlink:href="http://loop.frontiersin.org/people/888193/overview"/>
</contrib>
<contrib contrib-type="author">
<name><surname>Br&#x00F6;der</surname> <given-names>Lisa</given-names></name>
<xref ref-type="aff" rid="aff2"><sup>2</sup></xref>
<xref ref-type="aff" rid="aff4"><sup>4</sup></xref>
<uri xlink:href="http://loop.frontiersin.org/people/1239408/overview"/>
</contrib>
<contrib contrib-type="author">
<name><surname>Wagner</surname> <given-names>Dirk</given-names></name>
<xref ref-type="aff" rid="aff5"><sup>5</sup></xref>
<xref ref-type="aff" rid="aff6"><sup>6</sup></xref>
<uri xlink:href="http://loop.frontiersin.org/people/195547/overview"/>
</contrib>
<contrib contrib-type="author">
<name><surname>Knoblauch</surname> <given-names>Christian</given-names></name>
<xref ref-type="aff" rid="aff7"><sup>7</sup></xref>
<xref ref-type="aff" rid="aff8"><sup>8</sup></xref>
</contrib>
<contrib contrib-type="author">
<name><surname>Lantuit</surname> <given-names>Hugues</given-names></name>
<xref ref-type="aff" rid="aff1"><sup>1</sup></xref>
<xref ref-type="aff" rid="aff6"><sup>6</sup></xref>
</contrib>
<contrib contrib-type="author">
<name><surname>Beer</surname> <given-names>Christian</given-names></name>
<xref ref-type="aff" rid="aff7"><sup>7</sup></xref>
<xref ref-type="aff" rid="aff8"><sup>8</sup></xref>
</contrib>
<contrib contrib-type="author">
<name><surname>Sachs</surname> <given-names>Torsten</given-names></name>
<xref ref-type="aff" rid="aff3"><sup>3</sup></xref>
<uri xlink:href="http://loop.frontiersin.org/people/1259945/overview"/>
</contrib>
<contrib contrib-type="author">
<name><surname>Fritz</surname> <given-names>Michael</given-names></name>
<xref ref-type="aff" rid="aff1"><sup>1</sup></xref>
<uri xlink:href="http://loop.frontiersin.org/people/486425/overview"/>
</contrib>
<contrib contrib-type="author">
<name><surname>Tesi</surname> <given-names>Tommaso</given-names></name>
<xref ref-type="aff" rid="aff9"><sup>9</sup></xref>
</contrib>
<contrib contrib-type="author">
<name><surname>Koch</surname> <given-names>Boris P.</given-names></name>
<xref ref-type="aff" rid="aff10"><sup>10</sup></xref>
<xref ref-type="aff" rid="aff11"><sup>11</sup></xref>
<uri xlink:href="http://loop.frontiersin.org/people/698955/overview"/>
</contrib>
<contrib contrib-type="author">
<name><surname>Haghipour</surname> <given-names>Negar</given-names></name>
<xref ref-type="aff" rid="aff4"><sup>4</sup></xref>
<xref ref-type="aff" rid="aff12"><sup>12</sup></xref>
</contrib>
<contrib contrib-type="author">
<name><surname>Eglinton</surname> <given-names>Timothy I.</given-names></name>
<xref ref-type="aff" rid="aff4"><sup>4</sup></xref>
<uri xlink:href="http://loop.frontiersin.org/people/113546/overview"/>
</contrib>
<contrib contrib-type="author">
<name><surname>Strauss</surname> <given-names>Jens</given-names></name>
<xref ref-type="aff" rid="aff1"><sup>1</sup></xref>
<uri xlink:href="http://loop.frontiersin.org/people/375188/overview"/>
</contrib>
<contrib contrib-type="author">
<name><surname>Vonk</surname> <given-names>Jorien E.</given-names></name>
<xref ref-type="aff" rid="aff2"><sup>2</sup></xref>
<uri xlink:href="http://loop.frontiersin.org/people/134966/overview"/>
</contrib>
</contrib-group>
<aff id="aff1"><sup>1</sup><institution>Permafrost Research Unit, Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research</institution>, <addr-line>Potsdam</addr-line>, <country>Germany</country></aff>
<aff id="aff2"><sup>2</sup><institution>Department of Earth Sciences, Vrije Universiteit Amsterdam</institution>, <addr-line>Amsterdam</addr-line>, <country>Netherlands</country></aff>
<aff id="aff3"><sup>3</sup><institution>GFZ German Research Centre for Geosciences, Section Remote Sensing and Geoinformatics</institution>, <addr-line>Potsdam</addr-line>, <country>Germany</country></aff>
<aff id="aff4"><sup>4</sup><institution>Department of Earth Sciences, Swiss Federal Institute of Technology (ETH) Z&#x00FC;rich</institution>, <addr-line>Zurich</addr-line>, <country>Switzerland</country></aff>
<aff id="aff5"><sup>5</sup><institution>GFZ German Research Centre for Geosciences, Section Geomicrobiology</institution>, <addr-line>Potsdam</addr-line>, <country>Germany</country></aff>
<aff id="aff6"><sup>6</sup><institution>Institute of Geosciences, Universit&#x00E4;t Potsdam</institution>, <addr-line>Potsdam</addr-line>, <country>Germany</country></aff>
<aff id="aff7"><sup>7</sup><institution>Institute of Soil Science, Universit&#x00E4;t Hamburg</institution>, <addr-line>Hamburg</addr-line>, <country>Germany</country></aff>
<aff id="aff8"><sup>8</sup><institution>Center for Earth System Research and Sustainability, Universit&#x00E4;t Hamburg</institution>, <addr-line>Hamburg</addr-line>, <country>Germany</country></aff>
<aff id="aff9"><sup>9</sup><institution>Instituto di Scienze Polari &#x2013; National Research Council</institution>, <addr-line>Bologna</addr-line>, <country>Italy</country></aff>
<aff id="aff10"><sup>10</sup><institution>Biosciences Division, Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research</institution>, <addr-line>Bremerhaven</addr-line>, <country>Germany</country></aff>
<aff id="aff11"><sup>11</sup><institution>University of Applied Sciences</institution>, <addr-line>Bremerhaven</addr-line>, <country>Germany</country></aff>
<aff id="aff12"><sup>12</sup><institution>Laboratory of Ion Beam Physics, Swiss Federal Institute of Technology (ETH) Z&#x00FC;rich</institution>, <addr-line>Zurich</addr-line>, <country>Switzerland</country></aff>
<author-notes>
<fn fn-type="edited-by"><p>Edited by: Scott Raymond Dallimore, Geological Survey of Canada, Canada</p></fn>
<fn fn-type="edited-by"><p>Reviewed by: Raymond D. Ward, University of Brighton, United Kingdom; Baptiste Dafflon, Lawrence Berkeley National Laboratory, United States</p></fn>
<corresp id="c001">&#x002A;Correspondence: George Tanski, <email>george.tanski@awi.de</email></corresp>
<fn fn-type="other" id="fn004"><p>This article was submitted to Cryospheric Sciences, a section of the journal Frontiers in Earth Science</p></fn>
</author-notes>
<pub-date pub-type="epub">
<day>26</day>
<month>03</month>
<year>2021</year>
</pub-date>
<pub-date pub-type="collection">
<year>2021</year>
</pub-date>
<volume>9</volume>
<elocation-id>630493</elocation-id>
<history>
<date date-type="received">
<day>17</day>
<month>11</month>
<year>2020</year>
</date>
<date date-type="accepted">
<day>08</day>
<month>03</month>
<year>2021</year>
</date>
</history>
<permissions>
<copyright-statement>Copyright &#x00A9; 2021 Tanski, Br&#x00F6;der, Wagner, Knoblauch, Lantuit, Beer, Sachs, Fritz, Tesi, Koch, Haghipour, Eglinton, Strauss and Vonk.</copyright-statement>
<copyright-year>2021</copyright-year>
<copyright-holder>Tanski, Br&#x00F6;der, Wagner, Knoblauch, Lantuit, Beer, Sachs, Fritz, Tesi, Koch, Haghipour, Eglinton, Strauss and Vonk</copyright-holder>
<license xlink:href="http://creativecommons.org/licenses/by/4.0/"><p>This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.</p></license>
</permissions>
<abstract>
<p>Warming air and sea temperatures, longer open-water seasons and sea-level rise collectively promote the erosion of permafrost coasts in the Arctic, which profoundly impacts organic matter pathways. Although estimates on organic carbon (OC) fluxes from erosion exist for some parts of the Arctic, little is known about how much OC is transformed into greenhouse gases (GHGs). In this study we investigated two different coastal erosion scenarios on Qikiqtaruk &#x2013; Herschel Island (Canada) and estimate the potential for GHG formation. We distinguished between a <italic>delayed</italic> release represented by <italic>mud debris</italic> draining a coastal thermoerosional feature and a <italic>direct</italic> release represented by <italic>cliff debris</italic> at a low collapsing bluff. Carbon dioxide (CO<sub>2</sub>) production was measured during incubations at 4&#x00B0;C under aerobic conditions for two months and were modeled for four months and a full year. Our incubation results show that <italic>mud debris</italic> and <italic>cliff debris</italic> lost a considerable amount of OC as CO<sub>2</sub> (2.5 &#x00B1; 0.2 and 1.6 &#x00B1; 0.3% of OC, respectively). Although relative OC losses were highest in mineral <italic>mud debris</italic>, higher initial OC content and fresh organic matter in <italic>cliff debris</italic> resulted in a &#x223C;three times higher cumulative CO<sub>2</sub> release (4.0 &#x00B1; 0.9 compared to 1.4 &#x00B1; 0.1 mg CO<sub>2</sub> gdw<sup>&#x2013;1</sup>), which was further increased by the addition of seawater. After four months, modeled OC losses were 4.9 &#x00B1; 0.1 and 3.2 &#x00B1; 0.3% in set-ups without seawater and 14.3 &#x00B1; 0.1 and 7.3 &#x00B1; 0.8% in set-ups with seawater. The results indicate that a <italic>delayed</italic> release may support substantial cycling of OC at relatively low CO<sub>2</sub> production rates during long transit times <italic>onshore</italic> during the Arctic warm season. By contrast, <italic>direct</italic> erosion may result in a single CO<sub>2</sub> pulse and less substantial OC cycling <italic>onshore</italic> as transfer times are short. Once eroded sediments are deposited in the <italic>nearshore</italic>, highest OC losses can be expected. We conclude that the release of CO<sub>2</sub> from eroding permafrost coasts varies considerably between erosion types and residence time <italic>onshore</italic>. We emphasize the importance of a more comprehensive understanding of OC degradation during the coastal erosion process to improve thawed carbon trajectories and models.</p>
</abstract>
<kwd-group>
<kwd>Arctic</kwd>
<kwd>coastal erosion</kwd>
<kwd>carbon cycling</kwd>
<kwd>biogeochemistry</kwd>
<kwd>greenhouse gases</kwd>
<kwd>carbon dioxide</kwd>
<kwd>biomarkers</kwd>
</kwd-group><counts>
<fig-count count="5"/>
<table-count count="2"/>
<equation-count count="0"/>
<ref-count count="145"/>
<page-count count="20"/>
<word-count count="0"/>
</counts>
</article-meta>
</front>
<body>
<sec id="S1">
<title>Introduction</title>
<p>The Arctic is outpacing the global warming trend, which has severe impacts on ecosystems and biogeochemical pathways (<xref ref-type="bibr" rid="B24">Ciais et al., 2013</xref>; <xref ref-type="bibr" rid="B4">AMAP, 2017</xref>). With increasing temperatures, a cascade of environmental responses is initiated. Permafrost is warming and rapidly thawing, sea ice is declining in thickness and extent, seawater temperature is rising and wave and storm intensity are increasing (<xref ref-type="bibr" rid="B88">Manson and Solomon, 2007</xref>; <xref ref-type="bibr" rid="B100">Overeem et al., 2011</xref>; <xref ref-type="bibr" rid="B116">Schuur et al., 2015</xref>; <xref ref-type="bibr" rid="B12">Biskaborn et al., 2019</xref>; <xref ref-type="bibr" rid="B31">Dai et al., 2019</xref>). Arctic coastlines are particularly vulnerable to thaw and erosion due to the combined effects of environmental change (<xref ref-type="bibr" rid="B8">Barnhart et al., 2014</xref>; <xref ref-type="bibr" rid="B42">Fritz et al., 2017</xref>; <xref ref-type="bibr" rid="B96">Nielsen et al., 2020</xref>). Along with permafrost coasts, Arctic river deltas, estuaries and wetlands are increasingly impacted by sea level rise and glacier melt (<xref ref-type="bibr" rid="B10">Bendixen et al., 2017</xref>; <xref ref-type="bibr" rid="B138">Ward, 2020</xref>). These systems provide important ecosystem services (<xref ref-type="bibr" rid="B41">Forbes, 2019</xref>) but are currently facing changes in their sedimentation dynamics, which impacts organic matter pathways in the coastal zone (<xref ref-type="bibr" rid="B10">Bendixen et al., 2017</xref>; <xref ref-type="bibr" rid="B138">Ward, 2020</xref>). Permafrost coasts are the dominant interface between the northern landmass and the Arctic Ocean. Therefore, coastal erosion is a key driver for carbon and sediment transport into the Arctic Ocean (<xref ref-type="bibr" rid="B125">Stein and Macdonald, 2004</xref>; <xref ref-type="bibr" rid="B85">Macdonald et al., 2015</xref>; <xref ref-type="bibr" rid="B139">Wegner et al., 2015</xref>). Approximately two third of the Arctic coastline is composed of ice-rich and unconsolidated permafrost sediments prone to degradation, resulting in average erosion rates of 0.57 m yr<sup>&#x2013;1</sup> and extremes of &#x003E; 25 m yr<sup>&#x2013;1</sup> (<xref ref-type="bibr" rid="B6">Are et al., 2008</xref>; <xref ref-type="bibr" rid="B63">Jones et al., 2009</xref>, <xref ref-type="bibr" rid="B64">2018</xref>; <xref ref-type="bibr" rid="B79">Lantuit et al., 2012</xref>; <xref ref-type="bibr" rid="B50">G&#x00FC;nther et al., 2013</xref>, <xref ref-type="bibr" rid="B51">2015</xref>). With erosion, the massive reservoir of seasonally unfrozen and permafrost organic carbon (OC) in the Northern Hemisphere that stores &#x223C;1,300 Pg (10<sup>15</sup> g) OC is accessed at its coastal margins (<xref ref-type="bibr" rid="B79">Lantuit et al., 2012</xref>; <xref ref-type="bibr" rid="B59">Hugelius et al., 2014</xref>; <xref ref-type="bibr" rid="B92">McGuire et al., 2018</xref>). Recent studies estimate that the erosion of permafrost coasts transfers up to 430 Tg yr<sup>&#x2013;1</sup> of sediment and 14 Tg yr<sup>&#x2013;1</sup> of OC into the Arctic Ocean (<xref ref-type="bibr" rid="B139">Wegner et al., 2015</xref>). In the current understanding of Arctic carbon cycles, coastal erosion is considered to play a modest role in the transfer of OC from land to the Arctic Ocean (<xref ref-type="bibr" rid="B91">McGuire et al., 2009</xref>; <xref ref-type="bibr" rid="B125">Stein and Macdonald, 2004</xref>; <xref ref-type="bibr" rid="B85">Macdonald et al., 2015</xref>). Recent studies on abrupt permafrost erosion on land, however, suggest that OC is already fundamentally altered upon permafrost thaw, erosion and transport in aquatic systems on land, during which greenhouse gases (GHGs) can be released to the atmosphere (<xref ref-type="bibr" rid="B1">Abbott and Jones, 2015</xref>; <xref ref-type="bibr" rid="B87">Mann et al., 2015</xref>; <xref ref-type="bibr" rid="B124">Spencer et al., 2015</xref>; <xref ref-type="bibr" rid="B55">Heslop et al., 2017</xref>). During these erosional processes, the composition of OC is altered substantially with a substantial fraction potentially transformed into carbon dioxide (CO<sub>2</sub>) and methane (CH<sub>4</sub>), depending on oxygen availability (<xref ref-type="bibr" rid="B133">Vonk et al., 2012</xref>; <xref ref-type="bibr" rid="B117">Semiletov et al., 2016</xref>; <xref ref-type="bibr" rid="B130">Tanski et al., 2019</xref>). Yet, the degradation of OC from thawing permafrost coastlines has barely been considered (<xref ref-type="bibr" rid="B131">Vonk and Gustafsson, 2013</xref>; <xref ref-type="bibr" rid="B42">Fritz et al., 2017</xref>).</p>
<p>Coastal erosion releases large amounts of readily degradable permafrost OC, which is transported on relatively short transit times from land to sea with a high potential for GHG release (<xref ref-type="bibr" rid="B133">Vonk et al., 2012</xref>; <xref ref-type="bibr" rid="B130">Tanski et al., 2019</xref>). Once it enters the ocean, OC can be either further degraded within sediments and the water column or buried in marine sediments (<xref ref-type="bibr" rid="B134">Vonk et al., 2014</xref>; <xref ref-type="bibr" rid="B16">Br&#x00F6;der et al., 2018</xref>; <xref ref-type="bibr" rid="B28">Couture et al., 2018</xref>; <xref ref-type="bibr" rid="B48">Grotheer et al., 2020</xref>; <xref ref-type="bibr" rid="B65">Jong et al., 2020</xref>). Yet, little is known about the potential GHG formation during erosion as well as within the coastal <italic>nearshore</italic> corridor that receives the eroded sediments before entering the marine domain. While more comprehensive information on GHG production exist for terrestrial permafrost sites and the Arctic shelf, the coast itself remains sparsely investigated with GHG measurements only available for selected locations (<xref ref-type="bibr" rid="B133">Vonk et al., 2012</xref>; <xref ref-type="bibr" rid="B119">Shakhova et al., 2010</xref>, <xref ref-type="bibr" rid="B120">2015</xref>; <xref ref-type="bibr" rid="B66">Karlsson et al., 2015</xref>; <xref ref-type="bibr" rid="B99">Overduin et al., 2015</xref>; <xref ref-type="bibr" rid="B130">Tanski et al., 2019</xref>). Furthermore, the biogeochemical response of permafrost OC upon erosion may depend on coastal morphology and organic matter composition. Along coastlines with thermoerosional features and high bluffs, OC may encounter long transfer times <italic>onshore</italic> resulting in a <italic>delayed</italic> release to the sea with GHG formation already taking place <italic>onshore</italic> (<xref ref-type="fig" rid="F1">Figures 1A,B</xref>). In contrast, at sites with low bluffs (<xref ref-type="fig" rid="F1">Figures 1C,D</xref>), block-failure, active layer detachment slides or cliff collapse, OC may follow a more <italic>direct</italic> transfer pathway to the ocean. Thus, the type of erosion is strongly related to coastal morphology and may play a substantial role for the magnitude, timing and locus of GHG release. Local bathymetry and shelf morphology further determine the fate of OC and its potential for degradation offshore with rapid burial and sequestration limiting degradation but resuspension facilitating OC turnover in the <italic>nearshore</italic> (<xref ref-type="bibr" rid="B123">Solomon, 2005</xref>; <xref ref-type="bibr" rid="B133">Vonk et al., 2012</xref>; <xref ref-type="bibr" rid="B57">Hilton et al., 2015</xref>; <xref ref-type="bibr" rid="B124">Spencer et al., 2015</xref>; <xref ref-type="bibr" rid="B16">Br&#x00F6;der et al., 2018</xref>; <xref ref-type="bibr" rid="B48">Grotheer et al., 2020</xref>; <xref ref-type="bibr" rid="B65">Jong et al., 2020</xref>).</p>
<fig id="F1" position="float">
<label>FIGURE 1</label>
<caption><p>Examples of coastal erosion types along the Yukon coast (Canadian Arctic, Beaufort Sea). Thermoerosional features and high coastal bluffs may lead to organic matter degradation <italic>onshore</italic> due to longer transport times and a <italic>delayed</italic> release into the ocean <bold>(A,B)</bold>. Along low bluffs, permafrost debris collapses on the beach and is removed relatively quickly by waves via a more <italic>direct</italic> pathway into the <italic>nearshore</italic> zone <bold>(C,D)</bold>. Photographs were taken by A. Irrgang and G. Tanski in August 2015 on Qikiqtaruk &#x2013; Herschel Island <bold>(A,B)</bold> and the western Yukon coast <bold>(C,D)</bold>.</p></caption>
<graphic xlink:href="feart-09-630493-g001.tif"/>
</fig>
<p>Although geomorphologic studies on coastal erosion processes are manifold (e.g., <xref ref-type="bibr" rid="B8">Barnhart et al., 2014</xref>; <xref ref-type="bibr" rid="B51">G&#x00FC;nther et al., 2015</xref>; <xref ref-type="bibr" rid="B64">Jones et al., 2018</xref>), these studies do not target the OC fraction or relate morphology to the understanding of OC degradation and GHG dynamics. Bridging this information void on OC transformation during land-ocean-transit and the geochemical response during coastal erosion is key to better constrain biogeochemical pathways of OC in a warming Arctic and support Earth climate modeling approaches. The objective of this study is to investigate the CO<sub>2</sub> production at two contrasting erosion sites along Arctic permafrost coasts to better determine the pathways and turnover of OC during transport from land to sea.</p>
</sec>
<sec id="S2">
<title>Study Area</title>
<p>The study area Qikiqtaruk &#x2013; Herschel Island is situated &#x223C;2 km off the Yukon coast on the narrow Beaufort Sea Shelf (<xref ref-type="fig" rid="F2">Figure 2</xref>). The local climate conditions are polar continental with mean annual air temperatures of &#x2212;8.4&#x00B0;C (1995 to 2016) (<xref ref-type="bibr" rid="B25">Coch et al., 2018</xref>) and precipitation of &#x223C;170 mm yr<sup>&#x2013;1</sup> (<xref ref-type="bibr" rid="B20">Burn, 2012</xref>). During the peak of the warm season in July temperatures are on average 7.8&#x00B0;C with extremes of 30&#x00B0;C possible (<xref ref-type="bibr" rid="B20">Burn, 2012</xref>). The dominant wind directions are northwest and east with storms being frequent in August and September (<xref ref-type="bibr" rid="B37">Dunton et al., 2006</xref>). The island is a push moraine ridge formed &#x223C;18,000 to 23,000 years ago during the Wisconsin Glaciation with a maximum elevation of 183 m (<xref ref-type="bibr" rid="B107">Rampton, 1982</xref>; <xref ref-type="bibr" rid="B103">Pollard, 1990</xref>; <xref ref-type="bibr" rid="B43">Fritz et al., 2012</xref>). The sediments are composed of unconsolidated and fine-grained material of marine and glacigenic origin with glacier ice buried below the island (<xref ref-type="bibr" rid="B14">Blasco et al., 1990</xref>; <xref ref-type="bibr" rid="B43">Fritz et al., 2012</xref>). A rolling landscape incised by valleys with a lowland tundra vegetation dominated by <italic>graminoids</italic> and dwarf shrubs is typical for the island (<xref ref-type="bibr" rid="B121">Smith et al., 1989</xref>; <xref ref-type="bibr" rid="B68">Kennedy et al., 2001</xref>). The island is underlain with continuous permafrost with a shallow seasonal active layer of &#x223C;40&#x2013;60 cm in thickness, which has deepened by 15&#x2013;25 cm since the 1980s (<xref ref-type="bibr" rid="B74">Kokelj et al., 2002</xref>; <xref ref-type="bibr" rid="B21">Burn and Zhang, 2009</xref>). The surface sediments (up to &#x223C;1 m depth) on the island store &#x223C;35 kg OC m<sup>&#x2013;2</sup> with OC storage being lower in areas of mass wasting and higher at sites of accumulation (<xref ref-type="bibr" rid="B98">Obu et al., 2015</xref>; <xref ref-type="bibr" rid="B105">Ramage et al., 2019</xref>). Permafrost sediments mainly consist of mineral soils with elevated but strongly varying OC contents when cryoturbation occurs (average 6.0 &#x00B1; 4.7 wt% TOC; <xref ref-type="bibr" rid="B129">Tanski et al., 2017</xref>). The ground is very ice-rich with mean volumetric ground ice contents of 30&#x2013;60% and maximum volumes exceeding 90%, where massive ice beds and wedge ice are present (<xref ref-type="bibr" rid="B27">Couture and Pollard, 2015</xref>). The open water season lasts approximately from late June to early October with landfast ice being persistent in Herschel Basin and Thetis Bay (<xref ref-type="bibr" rid="B37">Dunton et al., 2006</xref>). The mean tides are 0.15 m and are superimposed to a 0.66 m annual tidal cycle in late July (<xref ref-type="bibr" rid="B60">Huggett et al., 1975</xref>; <xref ref-type="bibr" rid="B8">Barnhart et al., 2014</xref>). Regional sea-level rise proceeds at rates of 1.1&#x2013;3.5 mm yr<sup>&#x2013;1</sup> (<xref ref-type="bibr" rid="B89">Manson et al., 2005</xref>; <xref ref-type="bibr" rid="B62">James et al., 2014</xref>). The prevailing wind directions can influence water levels with northwest winds promoting a positive (higher water level) and eastern winds a negative storm surge (<xref ref-type="bibr" rid="B53">Hequette and Barnes, 1990</xref>; <xref ref-type="bibr" rid="B54">H&#x00E9;quette et al., 1995</xref>). The Mackenzie River plume has a strong influence on the coastal waters and transports warm water masses towards Qikiqtaruk &#x2013; Herschel island, which is amplified with easterly winds (<xref ref-type="bibr" rid="B37">Dunton et al., 2006</xref>). Qikiqtaruk &#x2013; Herschel Island is strongly impacted by thermoerosional processes and shoreline retreat. Retrogressive thaw slumps are ubiquitous and doubled in area since the 1950s (<xref ref-type="bibr" rid="B80">Lantuit and Pollard, 2005</xref>). On average, the island erodes at 0.68 m yr<sup>&#x2013;1</sup> (2000 to 2011), which is comparable to the average rates of the Yukon coast with 0.7 m yr<sup>&#x2013;1</sup> and the circum-Arctic with 0.57 m yr<sup>&#x2013;1</sup> (<xref ref-type="bibr" rid="B79">Lantuit et al., 2012</xref>; <xref ref-type="bibr" rid="B97">Obu et al., 2016</xref>; <xref ref-type="bibr" rid="B61">Irrgang et al., 2018</xref>). Extreme erosion rates of 14 and 22 m yr<sup>&#x2013;1</sup> were observed at low cliffs and active thaw slump systems, respectively (<xref ref-type="bibr" rid="B98">Obu et al., 2015</xref>; <xref ref-type="bibr" rid="B30">Cunliffe et al., 2019</xref>).</p>
<fig id="F2" position="float">
<label>FIGURE 2</label>
<caption><p>Study area Qikiqtaruk - Herschel Island off the Yukon coast in the western Canadian Arctic. The sampling sites <italic>mud debris</italic> (<italic>delayed</italic> release) and <italic>cliff debris</italic> (<italic>direct</italic> release) are situated in the south-eastern part of the island (close-up: middle panel). The <italic>mud debris</italic> was taken from a mud lobe draining a retrogressive thaw slump system (lower left panel) and the <italic>cliff debris</italic> from an eroding cliff at the rim of an alluvial fan (lower right panel). Exact sampling locations are displayed in <xref ref-type="supplementary-material" rid="FS1">Supplementary Figure 1</xref>. Plumes and a turbid <italic>nearshore</italic> water column are visible and indicate substantial input and transport of eroded sediments. Satellite imagery: Sentinel 2, RGB (27 July 2017).</p></caption>
<graphic xlink:href="feart-09-630493-g002.tif"/>
</fig>
</sec>
<sec id="S3" sec-type="materials|methods">
<title>Materials and Methods</title>
<sec id="S3.SS1">
<title>Field Work and Sampling</title>
<p>Permafrost erosion debris was sampled at two active coastal erosion sites on Qikiqtaruk &#x2013; Herschel Island in July and August 2017 (<xref ref-type="fig" rid="F2">Figure 2</xref>). <italic>Mud debris</italic> was sampled from a mud lobe draining a retrogressive thaw slump system (<xref ref-type="supplementary-material" rid="FS1">Supplementary Figure 1</xref>) representing the <italic>delayed</italic> release scenario, where eroded material has relatively long residence times <italic>onshore</italic> before release into the ocean. We targeted a retrogressive thaw slump since these features are ubiquitous along the coastline of the western Canadian Arctic (<xref ref-type="fig" rid="F1">Figures 1A</xref>, <xref ref-type="fig" rid="F2">2</xref>; <xref ref-type="bibr" rid="B101">Pelletier and Medioli, 2014</xref>; <xref ref-type="bibr" rid="B106">Ramage et al., 2017</xref>). This specific thaw slump was chosen because CO<sub>2</sub> degradation rates of permafrost from the thaw slumps headwall are known (<xref ref-type="bibr" rid="B130">Tanski et al., 2019</xref>) and are used as a permafrost reference for CO<sub>2</sub> release <italic>onshore</italic>. The mud lobe draining the thaw slump is a mix of thawed permafrost, collapsed active layer and melted massive ice (e.g., buried glacier ice, wedge ice), and can be either transported directly towards the ocean or stored temporarily in mud pools on annual or decadal time scales before release into the ocean (<xref ref-type="bibr" rid="B29">Cray and Pollard, 2015</xref>; <xref ref-type="bibr" rid="B129">Tanski et al., 2017</xref>). Five samples have been taken from the mud lobe at random locations and one composite sample, <italic>mud debris</italic> (MUD), mixed in equal amounts from the mud lobe samples under frozen conditions in the cold lab (<xref ref-type="table" rid="T1">Table 1</xref>).</p>
<table-wrap position="float" id="T1">
<label>TABLE 1</label>
<caption><p>Summary of bulk organic matter and lipid biomarkers (<italic>n</italic>-alkanes) for initial (<italic>T</italic> = 0) and incubated <italic>mud debris</italic> (MUD) and <italic>cliff debris</italic> (CD) samples after two months (<italic>T</italic> = 1).</p></caption>
<table cellspacing="5" cellpadding="5" frame="hsides" rules="groups">
<thead>
<tr>
<td valign="top" align="left"></td>
<td valign="top" align="center">Mud lobe</td>
<td valign="top" align="center">MUD (<italic>T</italic> = 0)</td>
<td valign="top" align="center">MUD (<italic>T</italic> = 1)</td>
<td valign="top" align="center">MUD&#x002A; (<italic>T</italic> = 1)</td>
<td valign="top" align="center">Cliff</td>
<td valign="top" align="center">CD (<italic>T</italic> = 0)</td>
<td valign="top" align="center">CD (<italic>T</italic> = 1)</td>
<td valign="top" align="center">CD&#x002A; (<italic>T</italic> = 1)</td>
</tr>
</thead>
<tbody>
<tr>
<td valign="top" align="left"><bold>Sedimentology</bold></td>
<td valign="top" align="center"><italic>n</italic> = 5</td>
<td valign="top" align="center"><italic>n</italic> = 1</td>
<td valign="top" align="center"><italic>n</italic> = 5</td>
<td valign="top" align="center"><italic>n</italic> = 3</td>
<td valign="top" align="center"><italic>n</italic> = 5</td>
<td valign="top" align="center"><italic>n</italic> = 1</td>
<td valign="top" align="center"><italic>n</italic> = 1</td>
<td valign="top" align="center"><italic>n</italic> = 3</td>
</tr>
<tr>
<td valign="top" align="left">Mineral SA (m<sup>2</sup> g<sup>&#x2013;1</sup>)</td>
<td valign="top" align="center">21.5</td>
<td valign="top" align="center">21.5</td>
<td valign="top" align="center">22.2</td>
<td valign="top" align="center">20.7</td>
<td valign="top" align="center">18.0</td>
<td valign="top" align="center">32.4</td>
<td valign="top" align="center">33.6</td>
<td valign="top" align="center">29.2</td>
</tr>
<tr>
<td/>
<td valign="top" align="center">&#x00B1; 0.6</td>
<td valign="top" align="center">&#x2013;</td>
<td valign="top" align="center">&#x00B1;1.1</td>
<td valign="top" align="center">&#x00B1; 2.9</td>
<td valign="top" align="center">&#x00B1;4.5</td>
<td valign="top" align="center">&#x2013;</td>
<td valign="top" align="center">&#x2013;</td>
<td valign="top" align="center">&#x00B1; 2.7</td>
</tr>
<tr>
<td valign="top" align="left">Clay (vol.%)</td>
<td valign="top" align="center">17.7</td>
<td valign="top" align="center">17.2</td>
<td valign="top" align="center">&#x2013;</td>
<td valign="top" align="center">&#x2013;</td>
<td valign="top" align="center">15.4</td>
<td valign="top" align="center">19.9</td>
<td valign="top" align="center">&#x2013;</td>
<td valign="top" align="center">&#x2013;</td>
</tr>
<tr>
<td/>
<td valign="top" align="center">&#x00B1; 1.5</td>
<td valign="top" align="center">&#x2013;</td>
<td/>
<td/>
<td valign="top" align="center">&#x00B1; 4.5</td>
<td valign="top" align="center">&#x2013;</td>
<td/>
<td/>
</tr>
<tr>
<td valign="top" align="left">Silt (vol.%)</td>
<td valign="top" align="center">69.1</td>
<td valign="top" align="center">71.7</td>
<td valign="top" align="center">&#x2013;</td>
<td valign="top" align="center">&#x2013;</td>
<td valign="top" align="center">70.4</td>
<td valign="top" align="center">66.7</td>
<td valign="top" align="center">&#x2013;</td>
<td valign="top" align="center">&#x2013;</td>
</tr>
<tr>
<td/>
<td valign="top" align="center">&#x00B1; 2.1</td>
<td valign="top" align="center">&#x2013;</td>
<td/>
<td/>
<td valign="top" align="center">&#x00B1; 6.9</td>
<td valign="top" align="center">&#x2013;</td>
<td/>
<td/>
</tr>
<tr>
<td valign="top" align="left">Sand (vol.%)</td>
<td valign="top" align="center">13.2</td>
<td valign="top" align="center">11.1</td>
<td valign="top" align="center">&#x2013;</td>
<td valign="top" align="center">&#x2013;</td>
<td valign="top" align="center">14.2</td>
<td valign="top" align="center">13.5</td>
<td valign="top" align="center">&#x2013;</td>
<td valign="top" align="center">&#x2013;</td>
</tr>
<tr>
<td/>
<td valign="top" align="center">&#x00B1; 3.3</td>
<td valign="top" align="center">&#x2013;</td>
<td/>
<td/>
<td valign="top" align="center">&#x00B1; 5.4</td>
<td valign="top" align="center">&#x2013;</td>
<td/>
<td/>
</tr>
<tr>
<td valign="top" align="left"><bold>Bulk organic matter</bold></td>
<td valign="top" align="center"><italic>n</italic> = 5</td>
<td valign="top" align="center"><italic>n</italic> = 1</td>
<td valign="top" align="center"><italic>n</italic> = 5</td>
<td valign="top" align="center"><italic>n</italic> = 5</td>
<td valign="top" align="center"><italic>n</italic> = 5</td>
<td valign="top" align="center"><italic>n</italic> = 1</td>
<td valign="top" align="center"><italic>n</italic> = 3</td>
<td valign="top" align="center"><italic>n</italic> = 3</td>
</tr>
<tr>
<td valign="top" align="left">TOC (wt%)</td>
<td valign="top" align="center">1.4</td>
<td valign="top" align="center">1.5</td>
<td valign="top" align="center">1.4</td>
<td valign="top" align="center">1.5</td>
<td valign="top" align="center">2.0</td>
<td valign="top" align="center">7.0</td>
<td valign="top" align="center">6.3</td>
<td valign="top" align="center">7.2</td>
</tr>
<tr>
<td/>
<td valign="top" align="center">&#x00B1; 0.03</td>
<td valign="top" align="center">&#x2013;</td>
<td valign="top" align="center">&#x00B1;0.0</td>
<td valign="top" align="center">&#x00B1; 0.0</td>
<td valign="top" align="center">&#x00B1;0.4</td>
<td valign="top" align="center">&#x2013;</td>
<td valign="top" align="center">&#x00B1; 0.6</td>
<td valign="top" align="center">&#x00B1;0.2</td>
</tr>
<tr>
<td valign="top" align="left">OC loading (mg m<sup>&#x2013;2</sup>)</td>
<td valign="top" align="center">0.6</td>
<td valign="top" align="center">0.7</td>
<td valign="top" align="center">0.6</td>
<td valign="top" align="center">0.8</td>
<td valign="top" align="center">1.1</td>
<td valign="top" align="center">2.1</td>
<td valign="top" align="center">1.9</td>
<td valign="top" align="center">2.5</td>
</tr>
<tr>
<td/>
<td valign="top" align="center">&#x00B1; 0.02</td>
<td valign="top" align="center">&#x2013;</td>
<td valign="top" align="center">&#x00B1;0.03</td>
<td valign="top" align="center">&#x00B1; 0.1</td>
<td valign="top" align="center">&#x00B1;0.3</td>
<td valign="top" align="center">&#x2013;</td>
<td valign="top" align="center">&#x00B1; 0.2</td>
<td valign="top" align="center">&#x00B1;0.2</td>
</tr>
<tr>
<td valign="top" align="left">TOC/TN (atomic ratio)</td>
<td valign="top" align="center">10.2</td>
<td valign="top" align="center">10.0</td>
<td valign="top" align="center">9.8</td>
<td valign="top" align="center">11.2</td>
<td valign="top" align="center">11.5</td>
<td valign="top" align="center">14.9</td>
<td valign="top" align="center">13.4</td>
<td valign="top" align="center">14.5</td>
</tr>
<tr>
<td/>
<td valign="top" align="center">&#x00B1; 0.2</td>
<td valign="top" align="center">&#x2013;</td>
<td valign="top" align="center">&#x00B1;0.3</td>
<td valign="top" align="center">&#x00B1; 0.6</td>
<td valign="top" align="center">&#x00B1;0.5</td>
<td valign="top" align="center">&#x2013;</td>
<td valign="top" align="center">&#x00B1; 0.7</td>
<td valign="top" align="center">&#x00B1;0.9</td>
</tr>
<tr>
<td valign="top" align="left">&#x03B4;<sup>13</sup>C-TOC (&#x2030;)</td>
<td valign="top" align="center">&#x2212;25.8</td>
<td valign="top" align="center">&#x2212;25.9</td>
<td valign="top" align="center">&#x2212;25.9</td>
<td valign="top" align="center">&#x2212;26.1</td>
<td valign="top" align="center">&#x2212;26.0</td>
<td valign="top" align="center">&#x2212;26.0</td>
<td valign="top" align="center">&#x2212;26.0</td>
<td valign="top" align="center">&#x2212;25.9</td>
</tr>
<tr>
<td/>
<td valign="top" align="center">&#x00B1; 0.1</td>
<td valign="top" align="center">&#x2013;</td>
<td valign="top" align="center">&#x00B1;0.0</td>
<td valign="top" align="center">&#x00B1; 0.5</td>
<td valign="top" align="center">&#x00B1;0.2</td>
<td valign="top" align="center">&#x2013;</td>
<td valign="top" align="center">&#x00B1; 0.1</td>
<td valign="top" align="center">&#x00B1;0.1</td>
</tr>
<tr>
<td valign="top" align="left">&#x0394;<sup>14</sup>C-TOC (&#x2030;)</td>
<td valign="top" align="center">&#x2212;800</td>
<td valign="top" align="center">&#x2212;834</td>
<td valign="top" align="center">&#x2212;836</td>
<td valign="top" align="center">&#x2212;800</td>
<td valign="top" align="center">&#x2212;499</td>
<td valign="top" align="center">&#x2212;261</td>
<td valign="top" align="center">&#x2212;253</td>
<td valign="top" align="center">&#x2212;221</td>
</tr>
<tr>
<td/>
<td valign="top" align="center">&#x00B1; 75</td>
<td valign="top" align="center">&#x2013;</td>
<td valign="top" align="center">&#x00B1;8</td>
<td valign="top" align="center">&#x00B1; 45</td>
<td valign="top" align="center">&#x00B1;100</td>
<td valign="top" align="center">&#x2013;</td>
<td valign="top" align="center">&#x00B1; 20</td>
<td valign="top" align="center">&#x00B1;2</td>
</tr>
<tr>
<td valign="top" align="left">Age (<sup>14</sup>C yr)</td>
<td valign="top" align="center">13,332</td>
<td valign="top" align="center">14,352</td>
<td valign="top" align="center">14,454</td>
<td valign="top" align="center">13,028</td>
<td valign="top" align="center">5679</td>
<td valign="top" align="center">2365</td>
<td valign="top" align="center">2283</td>
<td valign="top" align="center">1945</td>
</tr>
<tr>
<td/>
<td valign="top" align="center">&#x00B1; 2685</td>
<td valign="top" align="center">&#x2013;</td>
<td valign="top" align="center">&#x00B1;418</td>
<td valign="top" align="center">&#x00B1; 1631</td>
<td valign="top" align="center">&#x00B1;1896</td>
<td valign="top" align="center">&#x2013;</td>
<td valign="top" align="center">&#x00B1; 210</td>
<td valign="top" align="center">&#x00B1;19</td>
</tr>
<tr>
<td valign="top" align="left"><bold><italic>n</italic>-alkanes</bold></td>
<td valign="top" align="center"><italic>n</italic> = 5</td>
<td valign="top" align="center"><italic>n</italic> = 1</td>
<td valign="top" align="center"><italic>n</italic> = 5</td>
<td valign="top" align="center"><italic>n</italic> = 4</td>
<td valign="top" align="center"><italic>n</italic> = 5</td>
<td valign="top" align="center"><italic>n</italic> = 1</td>
<td valign="top" align="center"><italic>n</italic> = 2</td>
<td valign="top" align="center"><italic>n</italic> = 3</td>
</tr>
<tr>
<td valign="top" align="left">Total<sup>a</sup> (&#x03BC;g gdw<sup>&#x2013;1</sup>)</td>
<td valign="top" align="center">9.2</td>
<td valign="top" align="center">9.2</td>
<td valign="top" align="center">34.5</td>
<td valign="top" align="center">30.8</td>
<td valign="top" align="center">12.3</td>
<td valign="top" align="center">8.8</td>
<td valign="top" align="center">55.8</td>
<td valign="top" align="center">55.2</td>
</tr>
<tr>
<td/>
<td valign="top" align="center">&#x00B1; 3.4</td>
<td valign="top" align="center">&#x2013;</td>
<td valign="top" align="center">&#x00B1;4.5</td>
<td valign="top" align="center">&#x00B1; 0.9</td>
<td valign="top" align="center">&#x00B1;5.6</td>
<td valign="top" align="center">&#x2013;</td>
<td valign="top" align="center">&#x00B1; 6.9</td>
<td valign="top" align="center">&#x00B1;5.8</td>
</tr>
<tr>
<td valign="top" align="left">LMW<sup>b</sup> (&#x03BC;g gdw<sup>&#x2013;1</sup>)</td>
<td valign="top" align="center">0.4</td>
<td valign="top" align="center">0.4</td>
<td valign="top" align="center">6.0</td>
<td valign="top" align="center">5.0</td>
<td valign="top" align="center">0.7</td>
<td valign="top" align="center">0.5</td>
<td valign="top" align="center">8.0</td>
<td valign="top" align="center">6.6</td>
</tr>
<tr>
<td/>
<td valign="top" align="center">&#x00B1; 0.2</td>
<td valign="top" align="center">&#x2013;</td>
<td valign="top" align="center">&#x00B1;1.0</td>
<td valign="top" align="center">&#x00B1; 0.9</td>
<td valign="top" align="center">&#x00B1;0.7</td>
<td valign="top" align="center">&#x2013;</td>
<td valign="top" align="center">&#x00B1; 2.7</td>
<td valign="top" align="center">&#x00B1;1.2</td>
</tr>
<tr>
<td valign="top" align="left">HMW<sup>c</sup> (&#x03BC;g gdw<sup>&#x2013;1</sup>)</td>
<td valign="top" align="center">7.6</td>
<td valign="top" align="center">7.6</td>
<td valign="top" align="center">18.5</td>
<td valign="top" align="center">15.5</td>
<td valign="top" align="center">10.2</td>
<td valign="top" align="center">7.2</td>
<td valign="top" align="center">34.4</td>
<td valign="top" align="center">35.0</td>
</tr>
<tr>
<td/>
<td valign="top" align="center">&#x00B1; 2.9</td>
<td valign="top" align="center">&#x2013;</td>
<td valign="top" align="center">&#x00B1;2.0</td>
<td valign="top" align="center">&#x00B1; 3.4</td>
<td valign="top" align="center">&#x00B1;4.5</td>
<td valign="top" align="center">&#x2013;</td>
<td valign="top" align="center">&#x00B1; 4.2</td>
<td valign="top" align="center">&#x00B1;5.1</td>
</tr>
<tr>
<td valign="top" align="left">CPI<sup>d</sup> (C<sub>22&#x2013;34</sub>)</td>
<td valign="top" align="center">4.6</td>
<td valign="top" align="center">4.6</td>
<td valign="top" align="center">2.8</td>
<td valign="top" align="center">2.4</td>
<td valign="top" align="center">6.3</td>
<td valign="top" align="center">5.5</td>
<td valign="top" align="center">3.5</td>
<td valign="top" align="center">4.1</td>
</tr>
<tr>
<td/>
<td valign="top" align="center">&#x00B1; 0.2</td>
<td valign="top" align="center">&#x2013;</td>
<td valign="top" align="center">&#x00B1;0.3</td>
<td valign="top" align="center">&#x00B1; 0.2</td>
<td valign="top" align="center">&#x00B1;0.9</td>
<td valign="top" align="center">&#x2013;</td>
<td valign="top" align="center">&#x00B1; 0.1</td>
<td valign="top" align="center">&#x00B1;0.5</td>
</tr>
<tr>
<td valign="top" align="left">HMW/LMW<sup>e</sup></td>
<td valign="top" align="center">17.7</td>
<td valign="top" align="center">17.7</td>
<td valign="top" align="center">3.1</td>
<td valign="top" align="center">3.1</td>
<td valign="top" align="center">20.6</td>
<td valign="top" align="center">13.8</td>
<td valign="top" align="center">4.7</td>
<td valign="top" align="center">5.6</td>
</tr>
<tr>
<td/>
<td valign="top" align="center">&#x00B1; 5.3</td>
<td valign="top" align="center">&#x2013;</td>
<td valign="top" align="center">&#x00B1;0.4</td>
<td valign="top" align="center">&#x00B1; 0.5</td>
<td valign="top" align="center">&#x00B1;9.3</td>
<td valign="top" align="center">&#x2013;</td>
<td valign="top" align="center">&#x00B1; 1.1</td>
<td valign="top" align="center">&#x00B1;1.5</td>
</tr>
<tr>
<td valign="top" align="left">LMW-even/HMW-odd<sup>f</sup></td>
<td valign="top" align="center">0.14</td>
<td valign="top" align="center">0.14</td>
<td valign="top" align="center">0.77</td>
<td valign="top" align="center">0.92</td>
<td valign="top" align="center">0.14</td>
<td valign="top" align="center">0.16</td>
<td valign="top" align="center">0.52</td>
<td valign="top" align="center">0.46</td>
</tr>
<tr>
<td/>
<td valign="top" align="center">&#x00B1; 0.04</td>
<td valign="top" align="center">&#x2013;</td>
<td valign="top" align="center">&#x00B1;0.03</td>
<td valign="top" align="center">&#x00B1; 0.1</td>
<td valign="top" align="center">&#x00B1;0.08</td>
<td valign="top" align="center">&#x2013;</td>
<td valign="top" align="center">&#x00B1; 0.08</td>
<td valign="top" align="center">&#x00B1;0.13</td>
</tr>
</tbody>
</table>
<table-wrap-foot>
<attrib><italic>Values are given as mean with standard deviation (&#x00B1;) and sample size (n). The asterisk (&#x002A;) indicates incubation set-ups with seawater. &#x201C;Mud lobe&#x201D; and &#x201C;cliff&#x201D; samples are <italic>in situ</italic> samples and were not incubated. <sup><italic>a</italic></sup>&#x03A3; C<sub>14&#x2013;35</sub>. <sup><italic>b</italic></sup>&#x03A3; C<sub>14&#x2013;19</sub>. <sup><italic>c</italic></sup>&#x03A3; C<sub>23&#x2013;35</sub>. <sup><italic>d</italic></sup>CPI = 0.5 &#x03A3; (x<italic><sub><italic>i</italic></sub></italic> + x<italic><sub><italic>i</italic></sub></italic><sub>+</sub><sub>2</sub> + &#x2026; + x<italic><sub><italic>n</italic></sub></italic>)/&#x03A3; (x<italic><sub><italic>i</italic></sub></italic><sub>&#x2013;1</sub> + x<italic><sub><italic>i</italic></sub></italic><sub>+</sub><sub>1</sub> + &#x2026; + x<italic><sub><italic>n</italic></sub></italic><sub>&#x2013;1</sub>)+0.5 &#x03A3; (x<italic><sub><italic>i</italic></sub></italic> + x<italic><sub><italic>i</italic></sub></italic><sub>+</sub><sub>2</sub> + &#x2026; + x<italic><sub><italic>n</italic></sub></italic>)/&#x03A3; (x<italic><sub><italic>i</italic></sub></italic><sub>+</sub><sub>1</sub> + x<italic><sub><italic>i</italic></sub></italic><sub>+</sub><sub>3</sub> + &#x2026; + x<italic><sub><italic>n</italic></sub></italic><sub>+</sub><sub>1</sub>) with x being the concentration. <sup><italic>e</italic></sup>&#x03A3; C<sub>23&#x2013;35</sub>/&#x03A3;C<sub>14&#x2013;19</sub>. <sup><italic>f</italic></sup>&#x03A3; even C<sub>16&#x2013;20</sub>/&#x03A3; odd C<sub>27&#x2013;31</sub>.</italic></attrib>
</table-wrap-foot>
</table-wrap>
<p>The second site was a low permafrost cliff (&#x003C; 5 m height) located at an alluvial fan (<xref ref-type="fig" rid="F2">Figure 2</xref>), where <italic>cliff debris</italic> was collected. We chose this site to represent the <italic>direct</italic> release scenario with short residence time of eroded material <italic>onshore.</italic> This site was chosen since the erosion type is common along coasts with lower coastal bluffs (<xref ref-type="fig" rid="F1">Figures 1C,D</xref>, <xref ref-type="fig" rid="F2">2</xref>), where eroded material has shorter residence times <italic>onshore</italic> due to fast removal by wave action at high tides and storm surges (<xref ref-type="bibr" rid="B104">Radosavljevic et al., 2016</xref>; <xref ref-type="bibr" rid="B30">Cunliffe et al., 2019</xref>). We took five samples from the cliff face (Cliff, <xref ref-type="table" rid="T1">Table 1</xref>) and one sample from the <italic>cliff debris</italic> (CD) collected at the cliff toe assuming it to be an integrated signal of the <italic>cliff</italic> (<xref ref-type="table" rid="T1">Table 1</xref>). In contrast to MUD, no composite mix sample was used as we assumed that the cliff material was much more heterogeneous than the mud lobe. Thus, a mixing would have introduced an artificial bias as the mixing ratio was unclear. Surface seawater (SW) was collected approximately 2 km offshore, where water was clear and outside the range of visible erosion plumes.</p>
<p>All non-frozen samples from the mud debris and cliff debris (&#x223C;250&#x2013;500 g wet-weight) were taken with a pre-cleaned sampling spoon and stored in Whirl-pak bags. Samples were taken from approximately 5&#x2013;10 cm below the surface, at locations where material seemed to be well-mixed during the post-erosive transport process and therefore considered representative. All (frozen) permafrost samples from the cliff face were taken with a drill hammer (Hilti, Liechtenstein) after scraping off the potentially thawed material from the cliff surface. Samples (&#x223C;500 g wet-weight) were stored in Whirl-pak bags and stored frozen in a cooler immediately to avoid thaw. Seawater was taken from the sea surface in pre-rinsed (three times) 1L Nalgene bottles. All sampled materials, including seawater, were kept frozen at &#x2212;20&#x00B0;C until further processing in the laboratories.</p>
</sec>
<sec id="S3.SS2">
<title>Incubation Set-Ups</title>
<p>We simulated the erosion of <italic>mud debris</italic> and <italic>cliff debris onshore</italic> as well as in the <italic>nearshore</italic> in a laboratory incubation experiment at GFZ Potsdam to assess potential carbon pathways in this coastal transition zone. <italic>Onshore</italic> refers to incubation set-ups without seawater, mimicking erosion on land, while <italic>nearshore</italic> set-ups with seawater added were designed to mimic erosion into the seawater column. Frozen <italic>mud debris</italic> and <italic>cliff debris</italic> samples were homogenized and subsamples of &#x223C;20 g placed into 120 ml glass vials (autoclaved at 125&#x00B0;C) at &#x2212;15&#x00B0;C in a cold lab. The frozen seawater (SW) sample was melted slowly at 7&#x00B0;C in a cool (dark) room and shaken thoroughly. Just before the start of the incubation &#x223C;30 ml of unfiltered seawater was added to the glass vials with subsamples for the <italic>nearshore</italic> incubation set-ups. Afterwards, the vials were sealed with a rubber septum and the headspace (ca. 90 to 100 ml) was flushed with synthetic air (Linde, Germany) consisting of 20% oxygen (O<sub>2</sub>) and 80% nitrogen (N<sub>2</sub>). Vials were then placed in an incubator at 4&#x00B0;C shielded from light. Aerobic conditions were applied by flushing the headspace with synthetic air after each CO<sub>2</sub> measurement to represent venting and associated oxygen supply likely occurring during the erosion process <italic>onshore</italic> as well as in the immediate <italic>nearshore</italic>. The incubation period was set to two months to capture the initial period of highest CO<sub>2</sub> production (<xref ref-type="bibr" rid="B130">Tanski et al., 2019</xref>) and conducted at 4&#x00B0;C as it is close to the ambient Arctic sea surface temperatures and comparable to most published permafrost incubation studies (<xref ref-type="bibr" rid="B38">Dutta et al., 2006</xref>; <xref ref-type="bibr" rid="B82">Lee et al., 2012</xref>; <xref ref-type="bibr" rid="B113">Sch&#x00E4;del et al., 2014</xref>).</p>
</sec>
<sec id="S3.SS3">
<title>Hydrochemistry</title>
<p>Basic hydrochemical parameters pH and electrical conductivity were measured with a 3430 Digital Multiparameter meter (WTW, Germany) at room temperature at AWI Potsdam, Germany. Seawater was filtered with a 0.7 &#x03BC;m GF/F filter (Whatman, United Kingdom) and acidified with HCl (suprapur grade 30%) to pH 2. Dissolved organic carbon (DOC) and dissolved nitrogen (DN) concentrations were analyzed with a Shimadzu analyzer (Shimadzu, Japan) at AWI Bremerhaven, Germany.</p>
</sec>
<sec id="S3.SS4">
<title>Gas Measurements and Mass Calculation</title>
<p>CO<sub>2</sub> and CH<sub>4</sub> concentrations were measured with a 7890A GC (Agilent, United States) at GFZ Potsdam, Germany. Gas samples were taken on a regular basis (every other day during the first two weeks and two times a week afterwards) with a gastight syringe from the headspace of the vials and were immediately injected into the gas chromatograph. Afterwards, the headspace was flushed with synthetic air to reset aerobic conditions. After each measurement, glass vials were shaken to simulate mixing of sediments during mass movement <italic>onshore</italic> and by wave action and currents in the <italic>nearshore</italic>. The gas production was measured in parts per million (ppm) and normalized to gram dry weight (gdw<sup>&#x2013;1</sup>) of initial sediment. The total amount of CO<sub>2</sub> and CH<sub>4</sub> (&#x03BC;mol) was calculated following the methodology by <xref ref-type="bibr" rid="B71">Knoblauch et al. (2018)</xref> using gas concentration, headspace volume, water volume, pH, temperature and solubility including carbonate and bicarbonate concentrations for CO<sub>2</sub> calculations (<xref ref-type="bibr" rid="B93">Millero et al., 2007</xref>). All gas that remained in the glass vials after flushing was accounted for by assuming that CO<sub>2</sub> in the headspace was completely removed with flushing but dissolved inorganic carbon (DIC) remained in the glass vials. The derived amount of CO<sub>2</sub> in &#x03BC;mol was normalized to gdw<sup>&#x2013;1</sup> and recalculated into mg CO<sub>2</sub> gdw<sup>&#x2013;1</sup> using the molar mass (M) of CO<sub>2</sub> (44). In this study, we only report CO<sub>2</sub> as incubations conditions were aerobic.</p>
</sec>
<sec id="S3.SS5">
<title>Bulk Elemental and Isotopic Analyses</title>
<p>Sediments were weighed, freeze-dried and homogenized before chemical analysis. Elemental and stable carbon isotope analysis was conducted at AWI Potsdam, Germany, following established methodology (e.g., <xref ref-type="bibr" rid="B115">Schirrmeister et al., 2018</xref>). Total carbon (TC) and total nitrogen (TN) contents were measured with a VARIO EL III element analyzer (Elementar, Germany) and total organic carbon (TOC) with a VARIO MAX C analyzer (Elementar, Germany), both with a device-specific accuracy of &#x00B1; 0.1wt %. For stable carbon isotope (&#x03B4;<sup>13</sup>C-TOC), carbonates were removed from sediments with 1.3 molar hydrochloric acid (HCl) at 95&#x00B0;C for three hours. Stable carbon isotopes were then measured at the Isotope Facility at AWI Potsdam with a Delta-V-Advantage mass spectrometer (MS) (Thermo Fisher Scientific, Germany) coupled with a CONFLO IV gas mixing system. Stable carbon isotope contents are given in per mil (&#x2030;) relative to the standard Vienna Pee Dee Belemnite (VPDB) with an external error better than &#x00B1; 0.15&#x2030;. Radiocarbon (<sup>14</sup>C-TOC) measurements were performed at the Biogeoscience laboratories and the Laboratory for Ion Beam Physics at ETH Z&#x00FC;rich, Switzerland. Carbonates were removed by fumigation with HCl (37%, trace-metal purity) at 60&#x00B0;C for 72 h and samples measured on a coupled elemental analyzer-accelerator mass spectrometer (EA-AMS) system with a vario MICRO cube (Elementar, Germany) coupled to a Mini Carbon Dating System MICADAS (Ionplus, Switzerland) (e.g., <xref ref-type="bibr" rid="B110">Ruff et al., 2010</xref>). Radiocarbon values are reported in &#x0394;<sup>14</sup>C (&#x2030;) and <sup>14</sup>C-age as uncalibrated years (<sup>14</sup>C yr).</p>
</sec>
<sec id="S3.SS6">
<title>Grain Size Analysis</title>
<p>Grain size of sediment particles was analyzed at AWI Potsdam following an established methodology (<xref ref-type="bibr" rid="B114">Schirrmeister et al., 2020</xref>). Organic material was removed by adding 100ml of 3% H<sub>2</sub>O<sub>2</sub> over 3 to 6 weeks while on a shaking table. Organic-free sediments were then dispersed in 1L of water with dispersing agent (NH<sub>4</sub>OH) in an overhead shaker to de-cluster particles. Subsamples were then measured with a laser diffraction particle analyzer (Malvern Mastersizer 3000) with grain sizes measured between 0.375 to 1000 &#x03BC;m applying the Frauenhofer optical model. The cut-off value at 1000 &#x03BC;m was pre-set due to technical limitations of the particle analyzer.</p>
</sec>
<sec id="S3.SS7">
<title>Surface Area Analysis</title>
<p>Mineral surface area (SA) was measured to characterize the sediment structure of coastal debris. Approximately 1 g of subsampled sediment was combusted at 450&#x00B0;C for 12 h and rinsed with ultrapure water (MilliQ) to remove OC and salt, respectively. Afterwards, samples were freeze dried, degassed at 300&#x00B0;C with a vacuum applied for two hours and SA measured with a Nova 4200e SA analyzer (Quantachrome, United States) using the 6-point Brunauer&#x2013;Emmett&#x2013;Teller method (<xref ref-type="bibr" rid="B18">Brunauer et al., 1938</xref>).</p>
</sec>
<sec id="S3.SS8">
<title>Extraction and Analysis of Lipid Biomarkers</title>
<p>Lipid biomarkers (long-chain high molecular weight <italic>n</italic>-alkanes) were used to investigate the molecular composition of organic matter and its state of degradation (<xref ref-type="bibr" rid="B39">Eglinton and Hamilton, 1967</xref>). Lipid biomarkers were extracted at Vrije Universiteit Amsterdam, The Netherlands. Sediments (&#x223C;1 to 5 g) were extracted with a microwave digestion system MARS 6 (CEM, Germany) using dichloromethane (DCM) and methanol (MeOH) (9:1-volume ratio) at 100&#x00B0;C for 15 min. Microwave extracts were saponified with 10 ml potassium hydroxide (KOH, 0.5 M) in MeOH at 70&#x00B0;C for two hours. The neutral fraction was separated by wet-extraction with hexane following addition of 5 ml ultrapure water (MilliQ) with sodium chloride (NaCl). The neutral fraction was further separated into a-polar (containing the <italic>n</italic>-alkanes) and polar fractions by column chromatography using 5% deactivated silica (SiO<sub>2</sub>). The <italic>n</italic>-alkanes were analyzed with a gas chromatograph mass spectrometer (GC-MS, Agilent, United States) at the Institute of Polar Sciences in Bologna, Italy. The GC temperature program started at 55&#x00B0;C followed by a ramp up of 4 to 5&#x00B0;C min<sup>&#x2013;1</sup> to a maximum temperature 300 to 310&#x00B0;C for 15 to 20 min. Lipid biomarker concentrations are given in &#x03BC;g g<sup>&#x2013;1</sup> TOC. In this study concentrations are reported in &#x03BC;g gdw<sup>&#x2013;1</sup> to use the same normalization as for cumulative CO<sub>2</sub> production.</p>
</sec>
<sec id="S3.SS9">
<title>Bulk and Molecular Degradation Proxies</title>
<p>We used several established proxies to assess the degradation state of organic matter. Molar TOC/TN-ratios (atomic ratio) and &#x03B4;<sup>13</sup>C-TOC values were used as general indicators for bulk organic matter origin, preservation and degradation state (<xref ref-type="bibr" rid="B76">Kuhry and Vitt, 1996</xref>; <xref ref-type="bibr" rid="B78">Lamb et al., 2006</xref>; <xref ref-type="bibr" rid="B49">Gundelwein et al., 2007</xref>).</p>
<p>A low TOC/TN-ratio or relative decrease indicates degradation with a preferential mineralization of TOC and immobilization of TN by microbes coupled to CO<sub>2</sub> release under aerobic conditions (<xref ref-type="bibr" rid="B122">Sollins et al., 1984</xref>; <xref ref-type="bibr" rid="B126">Stevenson, 1994</xref>; <xref ref-type="bibr" rid="B127">Strauss et al., 2015</xref>). High &#x03B4;<sup>13</sup>C-TOC values (enriched in <sup>13</sup>C, i.e., less negative values) indicate decomposition as organic matter degradation discriminates against the lighter carbon component (<sup>12</sup>C), which results in a more negative &#x03B4;<sup>13</sup>C signature in the degrading fraction (<xref ref-type="bibr" rid="B56">Heyer et al., 1976</xref>; <xref ref-type="bibr" rid="B127">Strauss et al., 2015</xref>).</p>
<p>On a molecular level, we used the carbon preference index (CPI) for <italic>n</italic>-alkanes (ratio of odd over even-numbered C chain length homologues C<sub>22&#x2013;34</sub>) as indicator for the degree of microbial alteration of organic matter (<xref ref-type="bibr" rid="B15">Bray and Evans, 1961</xref>; <xref ref-type="bibr" rid="B69">Killops and Killops, 2004</xref>; <xref ref-type="bibr" rid="B127">Strauss et al., 2015</xref>). Living plants normally have CPI values greater 5 and decrease towards 1 with increasing maturity (<xref ref-type="bibr" rid="B109">Rielley et al., 1991</xref>; <xref ref-type="bibr" rid="B132">Vonk et al., 2010</xref>). High CPI values therefore indicate the presence of fresh organic matter, while mature or degraded organic matter displays lower CPI values. We further used high-molecular weight (HMW) to low-molecular weight (LMW) ratios of <italic>n</italic>-alkanes (&#x03A3;C<sub>23&#x2013;35</sub>/&#x03A3;C<sub>14&#x2013;19</sub>) as indicators for degradation since with ongoing degradation HMW compounds are broken down into LMW compounds (<xref ref-type="bibr" rid="B69">Killops and Killops, 2004</xref>). Additionally, we used the LMW-even to HMW-odd <italic>n</italic>-alkane ratio (C<sub>16</sub><sub>+</sub><sub>18</sub><sub>+</sub><sub>20</sub>/C<sub>27</sub><sub>+</sub><sub>29</sub><sub>+</sub><sub>31</sub>) with an increasing ratio indicating stronger microbial activity and degradation (<xref ref-type="bibr" rid="B47">Grimalt and Albaig&#x00E9;s, 1987</xref>; <xref ref-type="bibr" rid="B111">S&#x00E1;nchez-Garc&#x00ED;a et al., 2014</xref>).</p>
</sec>
<sec id="S3.SS10">
<title>CO<sub>2</sub> Production and Model</title>
<p>The total CO<sub>2</sub> production (cum. CO<sub>2</sub> gdw<sup>&#x2013;1</sup>) over 60 days and daily production rates (&#x03BC;g CO<sub>2</sub> gdw<sup>&#x2013;1</sup> day<sup>&#x2013;1</sup>) give information on the magnitude and rates of initial aerobic TOC decomposition in a given sample and are commonly used as degradability indicators (e.g., <xref ref-type="bibr" rid="B113">Sch&#x00E4;del et al., 2014</xref>). With the known total amount of CO<sub>2</sub> released we calculated the TOC loss in %.</p>
<p>CO<sub>2</sub> production was modeled four months and one year using an applied carbon decomposition model (<xref ref-type="bibr" rid="B5">Andr&#x00E9;n and K&#x00E4;tterer, 1997</xref>; <xref ref-type="bibr" rid="B72">Knoblauch et al., 2013</xref>). The model is based on a first-order kinetic function, which reflects changes in OC content over time and considers how fast OC pools are being decomposed. Degradation rates were estimated using a non-linear least squares approach with an integrated trust-region-reflective algorithm in MATLAB (MathWorks, United States). The cumulative CO<sub>2</sub> production measured during the incubation was used to calibrate the model. A logarithmic transformation was applied to estimate decomposition time of OC for four months and an entire year.</p>
</sec>
</sec>
<sec id="S4">
<title>Results and Discussion</title>
<sec id="S4.SS1">
<title>Organic Matter Origin and Composition</title>
<p>The composition of organic matter at the sampling sites was considerably different for most of the parameters considered (<xref ref-type="table" rid="T1">Table 1</xref>). The sediments at the investigated erosion sites mud lobe (<italic>n</italic> = 5) and cliff (<italic>n</italic> = 5) had TOC contents (1.4 &#x00B1; 0.03 and 2.0 &#x00B1; 0.4%), TOC/TN-ratios (10.2 &#x00B1; 0.2 and 11.5 &#x00B1; 0.5) and &#x03B4;<sup>13</sup>C concentrations (&#x2212;25.8 &#x00B1; 0.1 and &#x2212;26.0 &#x00B1; 0.2&#x2030;) typical for sediments containing terrestrial organic matter. Grain size structure was similar in both with the bulk of material (&#x223C;70 vol.%) composed of silt but was much more variable in the cliff (<xref ref-type="supplementary-material" rid="FS1">Supplementary Figure 2</xref>). The generally better sorting of mud lobe sediments may reflect hydrodynamic sorting during transport on land. The relatively high HMW/LMW <italic>n</italic>-alkane ratios (&#x03A3;C<sub>23&#x2013;35</sub>/&#x03A3;C<sub>14&#x2013;19</sub>) in mud lobe (17.7 &#x00B1; 5.3) and cliff (20.6 &#x00B1; 9.3) samples indicated good preservation of wax lipids from terrestrial plant matter (<xref ref-type="bibr" rid="B66">Karlsson et al., 2015</xref>; <xref ref-type="bibr" rid="B127">Strauss et al., 2015</xref>). This is supported by a relatively high (close to 5) CPI for long-chain <italic>n</italic>-alkanes (C<sub>22&#x2013;34</sub>) in mud lobe and cliff sediments (4.6 &#x00B1; 0.2 and 6.3 &#x00B1; 0.9, respectively). The lower TOC/TN-ratios and &#x03B4;<sup>13</sup>C values in the mud lobe in combination with lower HMW/LMW ratios and CPI for <italic>n</italic>-alkanes indicated slightly more matured organic matter in the mud lobe and better preserved organic matter in the cliff. The <sup>14</sup>C-age of OC varied considerably between the sites with relatively old organic matter in the mud lobe (13,332 &#x00B1; 2685 <sup>14</sup>C yr), most likely originating from deposition after the Wisconsin glaciation (<xref ref-type="bibr" rid="B103">Pollard, 1990</xref>; <xref ref-type="bibr" rid="B43">Fritz et al., 2012</xref>) and younger material in the cliff (5679 &#x00B1; 1896 <sup>14</sup>C yr), which was potentially deposited during Holocene warm periods (<xref ref-type="bibr" rid="B19">Burn, 1997</xref>; <xref ref-type="bibr" rid="B67">Kaufman et al., 2009</xref>; <xref ref-type="bibr" rid="B43">Fritz et al., 2012</xref>).</p>
<p>The <italic>mud debris</italic> (MUD, <italic>n</italic> = 1) was a mixed sample of the mud lobe deposits and thus showed the same organic matter composition and <sup>14</sup>C-age (14,352 <sup>14</sup>C yr). Compared to the mud lobe this indicates its origin from thawed old permafrost, which was likely augmented by active layer material, melted massive ice and old slump floor deposits during transport (<xref ref-type="bibr" rid="B80">Lantuit and Pollard, 2005</xref>; <xref ref-type="bibr" rid="B29">Cray and Pollard, 2015</xref>; <xref ref-type="bibr" rid="B129">Tanski et al., 2017</xref>). Mineral SA of <italic>mud debris</italic> was 21.5 m<sup>&#x2013;2</sup> gdw<sup>&#x2013;1</sup>, reflecting the presence of fine-grained sediments in the silt and clay size fraction making up &#x223C;72 and 17 vol.% (<xref ref-type="table" rid="T1">Table 1</xref>), respectively. In combination with relatively low TOC contents (1.5 wt%), the OC loading of <italic>mud debris</italic> was 0.7 mg OC m<sup>&#x2013;2</sup>. Collapsed active layer chunks from the slump headwall, which contained more modern and OC-rich sediments are usually (temporarily) deposited within the slump floor and mud lobe if not already transported offshore with the thaw stream draining the slump system (<xref ref-type="bibr" rid="B73">Kokelj et al., 2013</xref>; <xref ref-type="bibr" rid="B129">Tanski et al., 2017</xref>). During transport and mass wasting within the slump, a substantial portion of the organic matter was likely subject to degradation, resulting in the low TOC contents of the mud lobe and <italic>mud debris</italic> that was used in the incubation (<xref ref-type="bibr" rid="B29">Cray and Pollard, 2015</xref>; <xref ref-type="bibr" rid="B129">Tanski et al., 2017</xref>). This was supported by the much lower TOC content and TOC/TN-ratio (10.0) of the <italic>mud debris</italic> than the thaw slump headwall sediments (&#x223C;5 wt% and &#x003E; 15, respectively; <xref ref-type="bibr" rid="B129">Tanski et al., 2017</xref>). These slump sediments were also characterized by the presence of fresh organic matter, reflected by CPI values for <italic>n</italic>-alkanes of close to 30 (<xref ref-type="bibr" rid="B129">Tanski et al., 2017</xref>).</p>
<p>The <italic>cliff debris</italic> (CD, <italic>n</italic> = 1) collected from the permafrost cliff toe was markedly different in its organic matter composition, both compared to the cliff itself and the <italic>mud debris</italic>. The relatively high TOC content (7.0 wt%) and TOC/TN-ratio (14.9) in combination with its younger <sup>14</sup>C-age of 2365 <sup>14</sup>C yr and higher &#x03B4;<sup>13</sup>C values of &#x2212;26.0 &#x2030; indicate a strong contribution from relatively fresh and modern sources and C<sub>3</sub>-plant material that accumulated in the <italic>cliff debris</italic> (<xref ref-type="bibr" rid="B78">Lamb et al., 2006</xref>). The mineral SA of <italic>cliff debris</italic> was 32.4 m<sup>2</sup> g<sup>&#x2013;1</sup> and silt and clay volumes &#x223C;70 and 20 vol.%, respectively, indicating the presence of very fine-grained sediment fractions which in combination with high OC contents result in a high OC loading (2.1 mg OC m<sup>&#x2013;2</sup>). The relatively high CPI (5.5) as well as relatively high HMW/LMW ratios for <italic>n</italic>-alkanes (13.8) support the presence of relatively fresh organic matter in the <italic>cliff debris</italic> (<xref ref-type="bibr" rid="B109">Rielley et al., 1991</xref>; <xref ref-type="bibr" rid="B127">Strauss et al., 2015</xref>).</p>
</sec>
<sec id="S4.SS2">
<title>Constant vs. Rapid CO<sub>2</sub> Release</title>
<p>Considerable amounts of CO<sub>2</sub> were produced from <italic>mud debris</italic> and <italic>cliff debris</italic> over the two-months incubation period (<xref ref-type="fig" rid="F3">Figure 3</xref> and <xref ref-type="table" rid="T2">Table 2</xref>). The total amount of CO<sub>2</sub> produced was significantly different (ANOVA, <italic>p</italic> &#x003C; 0.05) between both, <italic>mud debris</italic> (<xref ref-type="fig" rid="F3">Figure 3A</xref>) and <italic>cliff debris</italic> (<xref ref-type="fig" rid="F3">Figure 3B</xref>), alongside with CO<sub>2</sub> production rates (<xref ref-type="supplementary-material" rid="FS1">Supplementary Figure 3</xref> and <xref ref-type="table" rid="T2">Table 2</xref>). <italic>Mud debris</italic> continuously released CO<sub>2</sub> at a relatively low rate with a maximum production of 50.6 &#x00B1; 4.5 &#x03BC;g CO<sub>2</sub> gdw<sup>&#x2013;1</sup> day<sup>&#x2013;1</sup> at the beginning, which decreased to 14.0 &#x00B1; 1.8 &#x03BC;g CO<sub>2</sub> gdw<sup>&#x2013;1</sup> day<sup>&#x2013;1</sup> at the end of the incubation, yielding a total of 1.4 &#x00B1; 0.1 mg CO<sub>2</sub> gdw<sup>&#x2013;1</sup> over a period of two months (<xref ref-type="fig" rid="F3">Figure 3A</xref>). Yet, when normalized to TOC content, the cumulative CO<sub>2</sub> production was almost three times higher from <italic>mud debris</italic> (93.4 &#x00B1; 7.6 mg CO<sub>2</sub> g TOC<sup>&#x2013;1</sup>) compared to <italic>cliff debris</italic> (36.1 &#x00B1; 12.7 mg CO<sub>2</sub> g TOC<sup>&#x2013;1</sup>). Outgassing of CO<sub>2</sub> from inorganic or petrogenic sources might have contributed to the observed CO<sub>2</sub> release as petrogenic OC is common in the study area and reactions of carbonates with sulphuric acid producing CO<sub>2</sub> were observed in thaw slump systems (<xref ref-type="bibr" rid="B46">Go&#x00F1;i et al., 2005</xref>; <xref ref-type="bibr" rid="B36">Drenzek et al., 2007</xref>; <xref ref-type="bibr" rid="B145">Zolkos et al., 2018</xref>). In contrast to the <italic>mud debris</italic>, <italic>cliff debris</italic> produced ca. three times more CO<sub>2</sub>, adding up to a total amount of 4.0 &#x00B1; 0.9 mg CO<sub>2</sub> gdw<sup>&#x2013;1</sup> over the two months of incubation, which was likely caused by the higher initial TOC content (7.0 wt%) and OC loading (2.1 mg OC m<sup>&#x2013;2</sup>; <xref ref-type="table" rid="T2">Table 2</xref> and <xref ref-type="fig" rid="F4">Figure 4</xref>). CO<sub>2</sub> production rates were fairly high within the first month. Maximum rates observed were 154 &#x00B1; 25.7 &#x03BC;g CO<sub>2</sub> gdw<sup>&#x2013;1</sup> day<sup>&#x2013;1</sup> and decreased to 34.2 &#x00B1; 12.5 &#x03BC;g CO<sub>2</sub> gdw<sup>&#x2013;1</sup> day<sup>&#x2013;1</sup> after two months of incubation.</p>
<fig id="F3" position="float">
<label>FIGURE 3</label>
<caption><p>Cumulative aerobic CO<sub>2</sub> production from incubated <italic>mud debris</italic> <bold>(A)</bold> and <italic>cliff debris</italic> <bold>(B)</bold>. <italic>Mud debris</italic> (MUD) and <italic>cliff debris</italic> (CD) were incubated without (black symbols) and with seawater (SW, blue symbols) for a duration of two months at 4&#x00B0;C under aerobic and dark conditions. Cumulative CO<sub>2</sub> production from permafrost (PF) is displayed as a local reference for CO<sub>2</sub> production from <italic>in situ</italic> permafrost without seawater (<xref ref-type="bibr" rid="B130">Tanski et al., 2019</xref>). The PF samples originate from the headwall of the thaw slump system from which the <italic>mud debris</italic> is released. The error bars show the standard deviation of the replicates used.</p></caption>
<graphic xlink:href="feart-09-630493-g003.tif"/>
</fig>
<table-wrap position="float" id="T2">
<label>TABLE 2</label>
<caption><p>Summary of observed and modeled cumulative CO<sub>2</sub> production and corresponding TOC loss in % as CO<sub>2</sub>-C after two months (60 days), regional open-water season of four months (120 days) and a full year (365 days) for incubation set-ups with <italic>mud debris</italic> (MUD), MUD with seawater (SW), <italic>cliff debris</italic> (CD) and CD with SW.</p></caption>
<table cellspacing="5" cellpadding="5" frame="hsides" rules="groups">
<thead>
<tr>
<td valign="top" align="left"></td>
<td valign="top" align="center">MUD</td>
<td valign="top" align="center">MUD + SW</td>
<td valign="top" align="center">CD</td>
<td valign="top" align="center">CD + SW</td>
</tr>
<tr>
<td/>
<td valign="top" align="center"><italic>n</italic> = 5</td>
<td valign="top" align="center"><italic>n</italic> = 5</td>
<td valign="top" align="center"><italic>n</italic> = 3</td>
<td valign="top" align="center"><italic>n</italic> = 3</td>
</tr>
</thead>
<tbody>
<tr>
<td valign="top" align="left"><bold>Incubation (60 days)</bold></td>
<td/>
<td/>
<td/>
<td/>
</tr>
<tr>
<td valign="top" align="left">Cum. CO<sub>2</sub> prod. (mg gdw<sup>&#x2013;1</sup>)</td>
<td valign="top" align="center">1.4</td>
<td valign="top" align="center">1.4</td>
<td valign="top" align="center">4.0</td>
<td valign="top" align="center">5.7</td>
</tr>
<tr>
<td/>
<td valign="top" align="center">&#x00B1; 0.1</td>
<td valign="top" align="center">&#x00B1;0.03</td>
<td valign="top" align="center">&#x00B1; 0.9</td>
<td valign="top" align="center">&#x00B1;0.4</td>
</tr>
<tr>
<td valign="top" align="left">Cum. CO<sub>2</sub> prod. (mg g TOC<sup>&#x2013;1</sup>)</td>
<td valign="top" align="center">93.4</td>
<td valign="top" align="center">96.4</td>
<td valign="top" align="center">36.1</td>
<td valign="top" align="center">51.0</td>
</tr>
<tr>
<td/>
<td valign="top" align="center">&#x00B1; 7.6</td>
<td valign="top" align="center">&#x00B1;2.3</td>
<td valign="top" align="center">&#x00B1; 12.7</td>
<td valign="top" align="center">&#x00B1;6.0</td>
</tr>
<tr>
<td valign="top" align="left">Cum. CO<sub>2</sub> prod. (&#x03BC;g m<sup>&#x2013;2</sup>)</td>
<td valign="top" align="center">62.9</td>
<td valign="top" align="center">76.3</td>
<td valign="top" align="center">119.8</td>
<td valign="top" align="center">195.3</td>
</tr>
<tr>
<td/>
<td valign="top" align="center">&#x00B1; 7.0</td>
<td valign="top" align="center">&#x00B1;10.3</td>
<td valign="top" align="center">&#x00B1; 26.2</td>
<td valign="top" align="center">&#x00B1;15.0</td>
</tr>
<tr>
<td valign="top" align="left">TOC loss (% as CO<sub>2</sub>-C)</td>
<td valign="top" align="center">2.5</td>
<td valign="top" align="center">2.6</td>
<td valign="top" align="center">1.6</td>
<td valign="top" align="center">2.2</td>
</tr>
<tr>
<td/>
<td valign="top" align="center">&#x00B1; 0.2</td>
<td valign="top" align="center">&#x00B1;0.1</td>
<td valign="top" align="center">&#x00B1; 0.3</td>
<td valign="top" align="center">&#x00B1;0.2</td>
</tr>
<tr>
<td valign="top" align="left">Max. CO<sub>2</sub> prod. rate (&#x03BC;g gdw<sup>&#x2013;1</sup> day<sup>&#x2013;1</sup>)</td>
<td valign="top" align="center">50.6</td>
<td valign="top" align="center">48.5</td>
<td valign="top" align="center">153.7</td>
<td valign="top" align="center">328.4</td>
</tr>
<tr>
<td/>
<td valign="top" align="center">&#x00B1; 4.5</td>
<td valign="top" align="center">&#x00B1;4.9</td>
<td valign="top" align="center">&#x00B1; 25.7</td>
<td valign="top" align="center">&#x00B1;99.3</td>
</tr>
<tr>
<td valign="top" align="left">End CO<sub>2</sub> prod. rate (&#x03BC;g gdw<sup>&#x2013;1</sup> day<sup>&#x2013;1</sup>)</td>
<td valign="top" align="center">14.0</td>
<td valign="top" align="center">23.7</td>
<td valign="top" align="center">34.2</td>
<td valign="top" align="center">29.5</td>
</tr>
<tr>
<td/>
<td valign="top" align="center">&#x00B1; 1.8</td>
<td valign="top" align="center">&#x00B1;1.4</td>
<td valign="top" align="center">&#x00B1; 12.5</td>
<td valign="top" align="center">&#x00B1;6.5</td>
</tr>
<tr>
<td valign="top" align="left"><bold>Model (120 days)</bold></td>
<td/>
<td/>
<td/>
<td/>
</tr>
<tr>
<td valign="top" align="left">Cum. CO<sub>2</sub> prod. (mg gdw<sup>&#x2013;1</sup>)</td>
<td valign="top" align="center">2.7</td>
<td valign="top" align="center">2.3</td>
<td valign="top" align="center">8.3</td>
<td valign="top" align="center">6.8</td>
</tr>
<tr>
<td/>
<td valign="top" align="center">&#x00B1; 0.05</td>
<td valign="top" align="center">&#x00B1;0.1</td>
<td valign="top" align="center">&#x00B1; 0.8</td>
<td valign="top" align="center">&#x00B1;1.6</td>
</tr>
<tr>
<td valign="top" align="left">TOC loss (% as CO<sub>2</sub>-C)</td>
<td valign="top" align="center">4.9</td>
<td valign="top" align="center">4.3</td>
<td valign="top" align="center">3.2</td>
<td valign="top" align="center">2.7</td>
</tr>
<tr>
<td/>
<td valign="top" align="center">&#x00B1; 0.1</td>
<td valign="top" align="center">&#x00B1;0.2</td>
<td valign="top" align="center">&#x00B1; 0.3</td>
<td valign="top" align="center">&#x00B1;0.6</td>
</tr>
<tr>
<td valign="top" align="left"><bold>Model (365 days)</bold></td>
<td/>
<td/>
<td/>
<td/>
</tr>
<tr>
<td valign="top" align="left">Cum. CO<sub>2</sub> prod. (mg gdw<sup>&#x2013;1</sup>)</td>
<td valign="top" align="center">7.8</td>
<td valign="top" align="center">6.1</td>
<td valign="top" align="center">18.7</td>
<td valign="top" align="center">17.7</td>
</tr>
<tr>
<td/>
<td valign="top" align="center">&#x00B1; 0.1</td>
<td valign="top" align="center">&#x00B1;0.5</td>
<td valign="top" align="center">&#x00B1; 2.1</td>
<td valign="top" align="center">&#x00B1;4.3</td>
</tr>
<tr>
<td valign="top" align="left">TOC loss (% as CO<sub>2</sub>-C)</td>
<td valign="top" align="center">14.3</td>
<td valign="top" align="center">11.1</td>
<td valign="top" align="center">7.3</td>
<td valign="top" align="center">6.9</td>
</tr>
<tr>
<td/>
<td valign="top" align="center">&#x00B1; 0.2</td>
<td valign="top" align="center">&#x00B1;0.9</td>
<td valign="top" align="center">&#x00B1; 0.8</td>
<td valign="top" align="center">&#x00B1;1.7</td>
</tr>
</tbody>
</table>
<table-wrap-foot>
<attrib><italic>Maximum and end daily CO<sub>2</sub> production rates are reported additionally. All values are given as mean &#x00B1; standard deviation with the sample size (<italic>n</italic>).</italic></attrib>
</table-wrap-foot>
</table-wrap>
<fig id="F4" position="float">
<label>FIGURE 4</label>
<caption><p>Cumulative CO<sub>2</sub> production normalized to gram dry weight (gdw) and %TOC loss as CO<sub>2</sub>-C at the end of the two month-incubation plotted against TOC content <bold>(A,B)</bold>, cumulative CO<sub>2</sub> production normalized to TOC content <bold>(C)</bold> and surface area <bold>(D)</bold> plotted against initial TOC content and surface area and cumulative CO<sub>2</sub> production normalized to gdw plotted against CPI <italic>n</italic>-alkanes <bold>(E)</bold> and HMW/LMW <italic>n</italic>-alkanes ratio <bold>(F)</bold>. Open symbols on the <italic>x</italic>-axis indicate samples from <italic>mud lobe</italic> and <italic>cliff</italic> that were not incubated to show the natural variability in the <italic>mud lobe</italic> and <italic>cliff</italic>. The <italic>mud debris</italic> (MUD) and <italic>cliff debris</italic> (CD) samples used for the incubation (<italic>T</italic> = 0) are indicated by the yellow symbols, incubated samples by the black symbols and incubated samples with seawater (SW) added by the blue symbols.</p></caption>
<graphic xlink:href="feart-09-630493-g004.tif"/>
</fig>
<p>The total amount of CO<sub>2</sub> released from <italic>mud debris</italic> mixed with seawater was virtually the same per gram sediment (1.4 &#x00B1; 0.1 mg CO<sub>2</sub> gdw<sup>&#x2013;1</sup>) and similar per g OC (96.4 &#x00B1; 2.3 mg CO<sub>2</sub> g TOC<sup>&#x2013;1</sup>) as without seawater added. The CO<sub>2</sub> production rates were also similar with a maximum of 48.5 &#x00B1; 4.9 &#x03BC;g CO<sub>2</sub> gdw<sup>&#x2013;1</sup> day<sup>&#x2013;1</sup> at the beginning (day 7) and 23.7 &#x00B1; 1.4 &#x03BC;g CO<sub>2</sub> gdw<sup>&#x2013;1</sup> day<sup>&#x2013;1</sup> at the end of the incubation. The most labile OC compounds may have been mineralized and released already as CO<sub>2</sub> during transport <italic>onshore</italic> before transfer with the mud lobe to the ocean (<xref ref-type="bibr" rid="B133">Vonk et al., 2012</xref>; <xref ref-type="bibr" rid="B3">Abbott et al., 2014</xref>; <xref ref-type="bibr" rid="B111">S&#x00E1;nchez-Garc&#x00ED;a et al., 2014</xref>). For <italic>cliff debris</italic> mixed with seawater, however, the total amount of CO<sub>2</sub> produced was significantly higher (5.7 &#x00B1; 0.4 mg CO<sub>2</sub> gdw<sup>&#x2013;1</sup>, ANOVA, <italic>p</italic> &#x003C; 0.05), corresponding to &#x223C;1.5 times more CO<sub>2</sub> released compared to without seawater added. This pattern was similar but less pronounced when normalized to g OC with 51.0 &#x00B1; 6.0 mg CO<sub>2</sub> g TOC<sup>&#x2013;1</sup>. The set-ups with seawater resulted in elevated CO<sub>2</sub> production rates with a maximum of 328 &#x00B1; 99.3 &#x03BC;g CO<sub>2</sub> gdw<sup>&#x2013;1</sup> day<sup>&#x2013;1</sup>. The production was particularly high during the first month, which likely indicates the rapid decomposition of freshly exposed and labile OC (<xref ref-type="bibr" rid="B72">Knoblauch et al., 2013</xref>; <xref ref-type="bibr" rid="B113">Sch&#x00E4;del et al., 2014</xref>). The production rate then decreased to 29.5 &#x00B1; 6.5 &#x03BC;g CO<sub>2</sub> gdw<sup>&#x2013;1</sup> day<sup>&#x2013;1</sup>, a similar value as for the set-up without seawater added. An increase in CO<sub>2</sub> production with addition of seawater was also observed in earlier studies for thawing permafrost from the thaw slump headwall, which might indicate a priming or co-metabolization effect (<xref ref-type="bibr" rid="B11">Bianchi, 2011</xref>; <xref ref-type="bibr" rid="B130">Tanski et al., 2019</xref>). Initial CO<sub>2</sub> production rates of <italic>mud debris</italic> were lower than those of <italic>in situ</italic> permafrost situated close to the sampling site in the thaw slump headwall (<xref ref-type="supplementary-material" rid="FS1">Supplementary Figure 3</xref>; <xref ref-type="bibr" rid="B130">Tanski et al., 2019</xref>). Yet, baseline production rates at the end of the two-month incubation period are slightly higher than from <italic>in situ</italic> permafrost. For <italic>cliff debris</italic>, initial as well as final CO<sub>2</sub> production rates were higher than for the permafrost reference site.</p>
<p>Following the CO<sub>2</sub> production in the first two months, the modeled CO<sub>2</sub> production and OC loss for the approximate length of the Arctic open-water season (&#x223C;four months) and an entire year, assuming that eroded sediments in the <italic>nearshore zone</italic> do not freeze-up anymore and that degradation is not only limited to the warm season, are substantially higher (<xref ref-type="table" rid="T2">Table 2</xref> and <xref ref-type="supplementary-material" rid="FS1">Supplementary Figures 4</xref>, <xref ref-type="supplementary-material" rid="FS1">5</xref>). Model results explain &#x223C;99% of the observed variations in CO<sub>2</sub> production for each individual sample and the residuals are usually unbiased and randomly scatter around zero. The only exceptions are residuals of cliff debris samples PI-14, PI-15 and PI-16 (<xref ref-type="supplementary-material" rid="FS1">Supplementary Figure 5</xref>), which show some pattern and hence should be dealt with cautiously. After four months, 2.7 &#x00B1; 0.05 mg CO<sub>2</sub> gdw<sup>&#x2013;1</sup> would be released from mud debris <italic>onshore</italic>, corresponding to a TOC loss of 4.9 &#x00B1; 0.1%, which is slightly lower for set-ups with seawater added. The CO<sub>2</sub> release from <italic>cliff debris onshore</italic> would be 8.3 &#x00B1; 0.8 mg CO<sub>2</sub> gdw<sup>&#x2013;1</sup> with TOC losses of 3.2 &#x00B1; 0.3%. This is also slightly lower when seawater is added. After one year upon erosion into the <italic>nearshore</italic>, <italic>mud debris</italic> would produce 6.1 &#x00B1; 0.5 mg CO<sub>2</sub> gdw<sup>&#x2013;1</sup> with 11.1 &#x00B1; 0.9% of the initial OC being lost. For <italic>cliff debris</italic> the CO<sub>2</sub> production would be much higher with 17.1 mg CO<sub>2</sub> gdw<sup>&#x2013;1</sup> corresponding to an OC loss of 6.9 &#x00B1; 1.7%. Model results based on set-ups without seawater show that the CO<sub>2</sub> release would be generally higher <italic>onshore</italic>. Yet, degradation is then limited to only &#x223C;four months per year, making the erosion and year-round degradation of OC in the <italic>nearshore</italic> much more effective. On decadal timescales microbes would decompose the more refractory carbon pools and thus support further CO<sub>2</sub> production at low rates, adding to the cumulative release of CO<sub>2</sub> (<xref ref-type="bibr" rid="B72">Knoblauch et al., 2013</xref>; <xref ref-type="bibr" rid="B113">Sch&#x00E4;del et al., 2014</xref>).</p>
<p>Experimental incubations that account for environmental conditions along eroding permafrost coastlines or continuous measurements of CO<sub>2</sub> or CH<sub>4</sub> from erosion sites are scarce in the Arctic, and our data are therefore challenging to put into context. GHG measurements are available from eroding permafrost cliffs at Muostakh Island (Siberian Arctic) with daily production rates ranging from 0.1 to 19.4 mg CO<sub>2</sub> m<sup>&#x2013;2</sup> day<sup>&#x2013;1</sup>, indicating intensive CO<sub>2</sub> release to the atmosphere in the warm season during erosion <italic>onshore</italic> (<xref ref-type="bibr" rid="B133">Vonk et al., 2012</xref>). For terrestrial permafrost sites elevated CO<sub>2</sub> concentrations of &#x003E; 1000 ppm were observed at thermoerosional features such as active layer detachment slides, gullies and thaw slumps, which also released substantial amounts of CH<sub>4</sub> (<xref ref-type="bibr" rid="B1">Abbott and Jones, 2015</xref>). These features might closely resemble the biogeochemical response of permafrost and modern OC to coastal erosion <italic>onshore</italic> as these processes are common along eroding coastlines as well (<xref ref-type="fig" rid="F1">Figures 1A,B</xref>). Once eroded into coastal waters, permafrost OC rapidly settles due to ballasting within mineral matrices but may further degrade during resuspension and lateral transport, thus further producing CO<sub>2</sub> (<xref ref-type="bibr" rid="B133">Vonk et al., 2012</xref>, <xref ref-type="bibr" rid="B134">2014</xref>; <xref ref-type="bibr" rid="B117">Semiletov et al., 2016</xref>; <xref ref-type="bibr" rid="B16">Br&#x00F6;der et al., 2018</xref>; <xref ref-type="bibr" rid="B130">Tanski et al., 2019</xref>; <xref ref-type="bibr" rid="B65">Jong et al., 2020</xref>).</p>
</sec>
<sec id="S4.SS3">
<title>Organic Matter Degradation vs. CO<sub>2</sub> Production</title>
<p>The release of CO<sub>2</sub> during the course of only two months indicates that organic matter is quickly degraded during the coastal erosion process. The production of CO<sub>2</sub> was positively correlated to TOC content and was higher in the OC-rich <italic>cliff debris</italic> than <italic>mud debris</italic> (<xref ref-type="fig" rid="F4">Figure 4A</xref>), which implies that CO<sub>2</sub> release is likely a function of the availability of fresh and degradable organic matter. This is supported by strong correlations between CO<sub>2</sub> production and initial <italic>n</italic>-alkane CPI values and TOC/TN-ratio (<xref ref-type="fig" rid="F4">Figure 4E</xref>, <xref ref-type="supplementary-material" rid="FS1">Supplementary Figure 6</xref> and <xref ref-type="table" rid="T1">Table 1</xref>). Yet, relative TOC losses (% as CO<sub>2</sub>-C) were significantly smaller (ANOVA, <italic>p &#x003C;</italic> 0.05) in <italic>cliff debris</italic> (1.6 &#x00B1; 0.3%) compared to <italic>mud debris</italic> (2.5 &#x00B1; 0.2%) (<xref ref-type="fig" rid="F4">Figure 4B</xref>). In general, the lower initial TOC content seems to correlate weakly with a higher (relative) TOC loss, suggesting that the old and OC-poor <italic>mud debris</italic> might be more prone to degradation than the relatively young and OC-rich <italic>cliff debris</italic> despite the lower total CO<sub>2</sub> release. This is expressed by the higher CO<sub>2</sub> production per g OC in <italic>mud debris</italic> (93.4 &#x00B1; 7.6 mg CO<sub>2</sub> g TOC<sup>&#x2013;1</sup>) compared to <italic>cliff debris</italic> (31.1 &#x00B1; 12.7 mg CO<sub>2</sub> g TOC<sup>&#x2013;1</sup>) (<xref ref-type="fig" rid="F4">Figures 4</xref>, <xref ref-type="fig" rid="F4">4C</xref>). In contrast, CO<sub>2</sub> production is higher from <italic>cliff debris</italic> when normalized to SA (119.8 &#x00B1; 26.2 &#x03BC;g CO<sub>2</sub> m<sup>&#x2013;2</sup>) compared to <italic>mud debris</italic> (62.9 &#x00B1; 7.0 &#x03BC;g CO<sub>2</sub> m<sup>&#x2013;2</sup>) (<xref ref-type="fig" rid="F4">Figure 4D</xref>) as the mineral OC-loading for <italic>cliff debris</italic> is higher than for <italic>mud debris</italic>. The production is even higher in set-ups with seawater added, particularly for <italic>cliff debris</italic> (195.3 &#x00B1; 15.0 &#x03BC;g CO<sub>2</sub> m<sup>&#x2013;2</sup>) compared to <italic>mud debris</italic> (119.8 &#x00B1; 26.2 &#x03BC;g CO<sub>2</sub> m<sup>&#x2013;2</sup>). The <italic>cliff debris</italic> site seems to be accumulating OC-rich fine-grained sediments with high OC content, mineral SA and clay portions, which finally result in the higher CO<sub>2</sub> release, whereas in the coarser <italic>mud debris</italic> this material may already have been removed offshore with the thaw stream or redeposited within the slump. With addition of seawater, CO<sub>2</sub> release from <italic>cliff debris</italic> increased, yet not significantly (ANOVA, <italic>p &#x003C;</italic> 0.05), alongside with TOC losses (2.2 &#x00B1; 0.2%), whereas for <italic>mud debris</italic> CO<sub>2</sub> production was similar for the set-ups with and without seawater added. Although the higher relative TOC losses from <italic>mud debris</italic> imply that it is more prone to degradation than the relatively young and OC-enriched <italic>cliff debris</italic>, the addition of seawater resulted in an increase of CO<sub>2</sub> production and corresponding TOC loss only in <italic>cliff debris</italic>. This might suggest that within <italic>mud debris</italic> the most labile compounds were already removed, and not available for further degradation in seawater. During transport within the slump system, this removal may have occurred via melting of massive ice that promoted leaching and liberation of more labile OC compounds and mineralization to CO<sub>2</sub> or CH<sub>4</sub> <italic>onshore</italic> (<xref ref-type="bibr" rid="B131">Vonk and Gustafsson, 2013</xref>; <xref ref-type="bibr" rid="B3">Abbott et al., 2014</xref>; <xref ref-type="bibr" rid="B87">Mann et al., 2015</xref>; <xref ref-type="bibr" rid="B129">Tanski et al., 2017</xref>). The relatively low mineral SA and OC loading of <italic>mud debris</italic> compared to <italic>cliff debris</italic> also suggest that the finer sediment fraction hosting OC may have been removed quickly from the <italic>mud debris</italic> with the thaw stream to the sea (<xref ref-type="bibr" rid="B65">Jong et al., 2020</xref>).</p>
<p>Incubated <italic>mud debris</italic> and <italic>cliff debris</italic> showed no significant changes in TOC contents, TOC/TN-ratios as well as in &#x03B4;<sup>13</sup>C-TOC and &#x0394;<sup>14</sup>C-TOC signatures (<xref ref-type="supplementary-material" rid="FS1">Supplementary Figure 6</xref>, <xref ref-type="table" rid="T1">Table 1</xref>). This is not surprising given the minor TOC losses (max. 2.5% of initial OC as CO<sub>2</sub>-C) during these short-term incubations of two months, and considering measurement uncertainties and natural heterogeneity of organic matter in individual samples. On a molecular level, however, organic matter degradation seems to be more pronounced (<xref ref-type="fig" rid="F4">Figure 4</xref>, <xref ref-type="supplementary-material" rid="FS1">Supplementary Figure 7</xref>, and <xref ref-type="table" rid="T1">Table 1</xref>). The CPI for <italic>n</italic>-alkanes decreased in all set-ups, indicating degradation of this organic matter fraction. In <italic>mud debris</italic> the CPI decreased from 4.6 &#x00B1; 0.2 to 2.8 &#x00B1; 0.3 and 2.4 &#x00B1; 0.2 without and with seawater added, respectively (<xref ref-type="fig" rid="F4">Figure 4E</xref>). This is similar, although less distinct, in <italic>cliff debris</italic>, where the CPI decreased from 5.5 to 3.5 &#x00B1; 0.1 and 4.1 &#x00B1; 0.5. Although the marked decrease of the HMW/LMW-ratio of <italic>n</italic>-alkanes mainly indicates the reworking of plant wax lipids (<xref ref-type="fig" rid="F4">Figure 4F</xref>), the increase of LMW-even to HMW-odd <italic>n</italic>-alkanes (<xref ref-type="supplementary-material" rid="FS1">Supplementary Figure 7</xref>) support the overall degradation of organic matter (<xref ref-type="bibr" rid="B111">S&#x00E1;nchez-Garc&#x00ED;a et al., 2014</xref>). Yet, LMW and HMW <italic>n</italic>-alkane concentrations increased in all set-ups indicating <italic>in situ</italic> production processes during the course of the incubation (<xref ref-type="table" rid="T1">Table 1</xref> and <xref ref-type="supplementary-material" rid="FS1">Supplementary Figure 8</xref>). Therefore, the used degradation proxies cannot unambiguously reflect the OC degradation process as production probably distorts the signal.</p>
<p>The concentration increase of LMW and HMW <italic>n</italic>-alkanes was highest for set-ups without seawater added. In the incubated <italic>mud debris</italic>, <italic>n</italic>-alkane concentrations increased for LMW <italic>n</italic>-alkanes from 0.4 to 6.0 &#x00B1; 1.0 (5.0 &#x00B1; 0.9 &#x03BC;g gdw<sup>&#x2013;1</sup> when mixed with seawater) and for HMW <italic>n</italic>-alkanes from 7.6 to 18.5 &#x00B1; 2.0 (15.5 &#x00B1; 3.4 &#x03BC;g gdw<sup>&#x2013;1</sup> with seawater). In <italic>cliff debris</italic>, this pattern was similar with LMW <italic>n</italic>-alkane concentrations increasing from 0.5 to 8.0 &#x00B1; 2.7 &#x03BC;g gdw<sup>&#x2013;1</sup> (6.6 &#x00B1; 1.2 &#x03BC;g gdw<sup>&#x2013;1</sup> with seawater). For the HMW <italic>n</italic>-alkane concentrations, there were virtually no differences between set-ups with or without seawater added. Concentrations increased from 7.2 to 34.4 &#x00B1; 4.2 and 35.0 &#x00B1; 5.1 &#x03BC;g gdw<sup>&#x2013;1</sup> with seawater added, respectively. While HMW <italic>n</italic>-alkane increase by up to four times during the incubation, LMW <italic>n</italic>-alkane concentrations increased up to 14 times compared to the initial concentrations (<xref ref-type="table" rid="T1">Table 1</xref>, <xref ref-type="supplementary-material" rid="FS1">Supplementary Figure 9</xref>). This substantial increase of <italic>n</italic>-alkanes under aerobic conditions, particularly LMW <italic>n</italic>-alkanes, may derive from heterotrophic microbial decomposers (<xref ref-type="bibr" rid="B83">Li et al., 2018</xref>; <xref ref-type="bibr" rid="B23">Chen et al., 2019</xref>). The predominance of even C-homologues in the LMW <italic>n</italic>-alkane fraction suggests a bacterial source and autochthonous production processes, which has been observed in estuarine and marine sediments (<xref ref-type="bibr" rid="B47">Grimalt and Albaig&#x00E9;s, 1987</xref>). Under anoxic conditions, these LMW <italic>n</italic>-alkane C-homologues can also derive from reduction of fatty acids (<xref ref-type="bibr" rid="B33">Debyser et al., 1977</xref>; <xref ref-type="bibr" rid="B32">Dastillung and Corbet, 1978</xref>). Yet, as aerobic conditions were applied during the experiment this process was probably restricted. Although no light was applied during the incubations, increases of LMW <italic>n</italic>-alkanes may have been also caused by algal growth as certain algae communities can thrive under extremely low radiance conditions (<xref ref-type="bibr" rid="B128">Suzuki et al., 1997</xref>). The lower even C-homologues in the HMW <italic>n</italic>-alkane fraction may point to the reduction of fatty acids or wax alcohols during degradation (<xref ref-type="bibr" rid="B77">Kvenvolden, 1970</xref>; <xref ref-type="bibr" rid="B140">Welte and Waples, 1973</xref>). Finally, contamination of lab equipment or by septa could also have been a potential source of <italic>n</italic>-alkanes. Yet, without further evidence the cause of the <italic>n</italic>-alkane increase remains speculative and biomarker from the post-incubation results should therefore be dealt with caution. However, the relatively low standard deviation of replicate analyses seems to rule out the random effect to be expected from septum leaching or contamination (<xref ref-type="supplementary-material" rid="FS1">Supplementary Figure 9</xref>).</p>
</sec>
<sec id="S4.SS4">
<title>DOC Release and Acidification</title>
<p>Over the course of the incubation, a minor portion of the sediment OC pool (&#x003C; 0.2%) was transferred into the DOC pool of the seawater. After the incubation DOC concentrations in seawater increased from initial 1.7 &#x00B1; 0.03 mg L<sup>&#x2013;1</sup> to 7.2 &#x00B1; 0.1 mg L<sup>&#x2013;1</sup> and 27.8 &#x00B1; 1.0 mg L<sup>&#x2013;1</sup> with addition of <italic>mud debris</italic> and <italic>cliff debris</italic>, respectively. The DOC increase in seawater mixed with <italic>cliff debris</italic> was &#x223C;four times higher mainly due to the higher initial TOC content (<xref ref-type="supplementary-material" rid="FS1">Supplementary Figure 10</xref> and <xref ref-type="supplementary-material" rid="FS1">Supplementary Table 2</xref>). This higher DOC release probably resulted in the higher CO<sub>2</sub> release as OC has to be in the form of DOC to pass cell membranes before metabolization by microbes (<xref ref-type="bibr" rid="B9">Battin et al., 2008</xref>; <xref ref-type="bibr" rid="B131">Vonk and Gustafsson, 2013</xref>). Thus, when normalized to initial TOC content, DOC yields for <italic>mud debris</italic> and <italic>cliff debris</italic> after 2 month of incubation are similar with 3.1 &#x00B1; 0.1 and 3.6 &#x00B1; 0.1 mg g<sup>&#x2013;1</sup> OC, respectively. This indicates that DOC leaching and adsorption processes with mineral surfaces are of similar magnitude for both debris types during the two months of incubation (<xref ref-type="bibr" rid="B95">Neff and Asner, 2001</xref>; <xref ref-type="bibr" rid="B84">Littlefair et al., 2017</xref>). Higher DOC yields (6.6 &#x00B1; 1.7 and 7.4 &#x00B1; 1.4 mg g<sup>&#x2013;1</sup> OC, respectively) have been observed in seawater mixed with mineral and organic-rich permafrost in previous studies, where permafrost had similar initial TOC contents (1.7 &#x00B1; 0.2 and 7.8 &#x00B1; 0.7 wt%, respectively) to <italic>mud debris</italic> and <italic>cliff debris</italic>, yet the incubation period was twice as long (<xref ref-type="supplementary-material" rid="FS1">Supplementary Figure 10</xref>; <xref ref-type="bibr" rid="B130">Tanski et al., 2019</xref>). This suggests that leaching capacity and DOC yield may increase over time or that DOC components prone to leaching were already leached from <italic>mud debris</italic> and <italic>cliff debris</italic> during transport <italic>onshore</italic>. A dynamic balance of hydrolysis from particulate OC to DOC and subsequent mineralization into CO<sub>2</sub> was probably established within days (<xref ref-type="bibr" rid="B75">Kristensen et al., 1995</xref>). This is indicated by stabilization of CO<sub>2</sub> production rates after the initial CO<sub>2</sub> release during the first weeks stemming from rapid mineralization of the most labile compounds. Leaching of labile compounds from plant debris or mineral-bound OC is more likely for <italic>cliff debris</italic> since labile compounds were probably still available as transit time <italic>onshore</italic> until accumulation at the cliff toe was short (<xref ref-type="bibr" rid="B35">Dou et al., 2008</xref>; <xref ref-type="bibr" rid="B13">Blair and Aller, 2012</xref>; <xref ref-type="bibr" rid="B135">Vonk et al., 2015</xref>). In combination with the initial liberation of labile DOC compounds, priming and co-metabolization might have caused the initial increase of CO<sub>2</sub> production in <italic>cliff debris</italic> mixed with seawater (<xref ref-type="bibr" rid="B11">Bianchi, 2011</xref>). Input of additional nutrients with seawater might have promoted decomposition of organic matter (<xref ref-type="bibr" rid="B86">Mack et al., 2004</xref>). Furthermore, input of nutrients from the adjacent cliffs topsoil would have likely supported microbial metabolic efficiency in the <italic>cliff debris</italic> (<xref ref-type="bibr" rid="B22">Chen et al., 2018</xref>) and thus CO<sub>2</sub> production. The increase of DOC concentrations in unfiltered seawater controls from 1.7 &#x00B1; 0.0 to 2.6 &#x00B1; 1.0 mg L<sup>&#x2013;1</sup> (<xref ref-type="supplementary-material" rid="FS1">Supplementary Table 2</xref>) indicate potential production during the incubations and may support the increase of LMW <italic>n</italic>-alkanes observed. This could have further increased the DOC content in the seawater, which was mixed with <italic>mud debris</italic> and <italic>cliff debris</italic> and influences the CO<sub>2</sub> release from the seawater.</p>
<p>In combination with increasing DOC concentrations, a substantial acidification of the seawater mixed with <italic>mud debris</italic> and <italic>cliff debris</italic> from pH 8.2 to 7.0 &#x00B1; 0.1 and 7.0 &#x00B1; 0.0, respectively, was observed (<xref ref-type="supplementary-material" rid="FS1">Supplementary Figure 10</xref> and <xref ref-type="supplementary-material" rid="FS1">Supplementary Table 2</xref>). This could have been caused by a low pH of soil organic matter within eroded debris or dissolution of CO<sub>2</sub> produced from the debris in seawater. An even stronger pH decrease from 8.4 &#x00B1; 0.1 to 5.2 &#x00B1; 0.2, was observed during a longer incubation experiment with organic-rich permafrost mixed with seawater, which was likely caused by the low initial pH (6.1 &#x00B1; 0.1) of the permafrost and a high DOC yield (<xref ref-type="supplementary-material" rid="FS1">Supplementary Figure 10</xref>; <xref ref-type="bibr" rid="B130">Tanski et al., 2019</xref>). Depending on the ratio of sediment to seawater, acidification could occur during erosion, which was shown for coastal waters in the Siberian Arctic that receive large amounts of permafrost OC. This, in turn, could result in elevated <italic>p</italic>CO<sub>2</sub> and outgassing to the atmosphere (<xref ref-type="bibr" rid="B118">Semiletov et al., 2013</xref>, <xref ref-type="bibr" rid="B117">2016</xref>).</p>
</sec>
<sec id="S4.SS5">
<title>Incubations Cannot Account for Dynamic <italic>in situ</italic> Environmental Conditions</title>
<p>The measured CO<sub>2</sub> release rates and OC losses from eroded organic matter were obtained through experimental settings with low constant temperatures, maximum oxygen availability and dark conditions, which are classically used to study permafrost thaw through gradual active layer deepening (e.g., <xref ref-type="bibr" rid="B82">Lee et al., 2012</xref>; <xref ref-type="bibr" rid="B72">Knoblauch et al., 2013</xref>; <xref ref-type="bibr" rid="B113">Sch&#x00E4;del et al., 2014</xref>). The CO<sub>2</sub> release observed under laboratory conditions would very likely differ from <italic>in situ</italic> observations. Yet, for coastal erosion processes onshore and in the nearshore coastal waters, environmental conditions are far from stable. The soil-to-water ratio under natural conditions is much lower resulting in a lower acidification as observed in the incubation vials. With a pH typical for ambient seawater (&#x223C;8.2), CO<sub>2</sub> production rates would probably remain similar but carbon storage in seawater would shift towards bicarbonate and carbonate (<xref ref-type="bibr" rid="B143">Wolf-Gladrow et al., 2007</xref>). The most important environmental parameters affecting the CO<sub>2</sub> production under natural conditions are most likely temperature and oxygen availability. Incubation experiments carried out at 15 or 16 &#x00B0;C (compared to 4 &#x00B0;C) showed that CO<sub>2</sub> production increased substantially compared to lower temperatures &#x003C;4 &#x00B0;C (<xref ref-type="bibr" rid="B38">Dutta et al., 2006</xref>; <xref ref-type="bibr" rid="B82">Lee et al., 2012</xref>; <xref ref-type="bibr" rid="B72">Knoblauch et al., 2013</xref>; <xref ref-type="bibr" rid="B112">Sch&#x00E4;del et al., 2016</xref>; <xref ref-type="bibr" rid="B130">Tanski et al., 2019</xref>). For our study area Qikiqtaruk - Herschel Island temperatures in the coastal waters depend on wind direction and coastal orientation and range between &#x223C;5 and 14&#x00B0;C during the warm season (<xref ref-type="bibr" rid="B70">Klein et al., 2019</xref>). This fits with observations from <xref ref-type="bibr" rid="B30">Cunliffe et al. (2019)</xref>, which reported seawater surface temperatures between &#x223C;6 to 10&#x00B0;C close to our sampling sites. During the warm season, air temperatures onshore are on average &#x223C;8&#x00B0;C and soil temperatures in the active layer between 4.2 and 6.6&#x00B0;C with maximum values of 9.8&#x00B0;C (<xref ref-type="bibr" rid="B20">Burn, 2012</xref>; <xref ref-type="bibr" rid="B144">Wolter et al., 2016</xref>). The higher ambient temperatures would result in stronger OM mineralization rates onshore and in the nearshore under natural conditions compared to our incubation results. Using a Q10 value of 2 from <xref ref-type="bibr" rid="B112">Sch&#x00E4;del et al. (2016)</xref>, an average air temperature of &#x223C;8&#x00B0;C, and a conservative seawater temperature of &#x223C;6&#x00B0;C, the CO<sub>2</sub> production rates measured at 4&#x00B0;C would be &#x223C;32% higher onshore at 8&#x00B0;C and &#x223C;15% higher in the nearshore at 6&#x00B0;C. With warmer <italic>in situ</italic> seawater temperatures the solubility of CO<sub>2</sub> also decreases which further promotes the release of CO<sub>2</sub> to the atmosphere from coastal waters.</p>
<p>Another important driving factor for OC mineralization is the availability of oxygen. In contrast to the steady aerobic conditions during our incubation, which support efficient OC degradation and CO<sub>2</sub> production, less efficient anaerobic CO<sub>2</sub> and CH<sub>4</sub> production may apply onshore, where oxygen cannot penetrate deeper layers of the mud debris and cliff debris or under water-logged conditions. Under anaerobic conditions, OC mineralization is about 3 times slower than under aerobic conditions (<xref ref-type="bibr" rid="B112">Sch&#x00E4;del et al., 2016</xref>; <xref ref-type="bibr" rid="B71">Knoblauch et al., 2018</xref>). This would result in an approximately three times lower theoretical OC loss of in mud debris and cliff debris (0.4 and 1.3%, respectively), where anaerobic conditions apply under natural condition, compared to the observed OC loss of 1.1 and 3.9%, respectively, under aerobic conditions in the experiment. In contrast to less efficient anaerobic mineralization of OM, drainage and drying of eroded material onshore could further increase oxygen penetration into eroded debris and support aerobic carbon mineralization. Inter or intra-annual refreezing cycles could further enhance macro-pore spaces and infiltration capacity of sediments (<xref ref-type="bibr" rid="B34">Ding et al., 2019</xref>). This could supply oxygen to pore spaces or further mechanical destruction of organo-mineral bonds, which may cause short-lived CO<sub>2</sub> pulses (<xref ref-type="bibr" rid="B13">Blair and Aller, 2012</xref>; <xref ref-type="bibr" rid="B58">H&#x00F6;fle et al., 2013</xref>; <xref ref-type="bibr" rid="B136">Walz et al., 2017</xref>). Additionally, drying and rewetting cycles (caused by rain, waves or high tides) could also further amplify CO<sub>2</sub> production by microbial mineralization of OC and weakening the physical protection of the soil matrix (<xref ref-type="bibr" rid="B40">Fierer and Schimel, 2003</xref>).</p>
<p>During transport onshore or in the nearshore water column, photo-oxidation can promote DOC degradation (by up to 40%), which is coupled to CO<sub>2</sub> release (<xref ref-type="bibr" rid="B26">Cory et al., 2013</xref>). The input of fresh nutrients, organic matter or plant litter from erosion itself, surface runoff or seawater could trigger priming effects and co-metabolism of recalcitrant organic matter combined from active layer and permafrost, thus further promoting CO<sub>2</sub> release (<xref ref-type="bibr" rid="B3">Abbott et al., 2014</xref>; <xref ref-type="bibr" rid="B142">Wild et al., 2014</xref>, <xref ref-type="bibr" rid="B141">2016</xref>; <xref ref-type="bibr" rid="B1">Abbott and Jones, 2015</xref>; <xref ref-type="bibr" rid="B136">Walz et al., 2017</xref>; <xref ref-type="bibr" rid="B71">Knoblauch et al., 2018</xref>). Light conditions could further promote those priming effects in the ocean between produced algal exudates and eroded OC (<xref ref-type="bibr" rid="B11">Bianchi, 2011</xref>). The majority of these factors would likely lead to higher OC loss and CO<sub>2</sub> production under natural coastal erosion conditions compared to the experimental incubations set-ups employed in this study. Once deposited in nearshore sediments, OM degradation pathways depend on sedimentation rates and oxygen penetration depth. In our study region sedimentation rates range from 0.1 mm yr<sup>&#x2013;1</sup> offshore to 2 mm yr<sup>&#x2013;1</sup> in the vicinity of the Mackenzie River but can reach up to 0.33 cm yr<sup>&#x2013;1</sup> at shelf locations which promote deposition (<xref ref-type="bibr" rid="B52">Harper and Penland, 1982</xref>; <xref ref-type="bibr" rid="B48">Grotheer et al., 2020</xref>). In combination with an oxygen penetration depth of a few mm to cm in marine sediments (<xref ref-type="bibr" rid="B44">Glud, 2008</xref>; <xref ref-type="bibr" rid="B7">Arndt et al., 2013</xref>), we would assume that aerobic conditions similar as in our experiment would apply for eroded and deposited sediments within the first years of deposition and during resuspension, winnowing or longshore transport. In subsequent years, anaerobic conditions may gradually take over in the initially deposited sediments, limiting efficient OC degradation and promoting OC burial on geological time scales (<xref ref-type="bibr" rid="B57">Hilton et al., 2015</xref>; <xref ref-type="bibr" rid="B16">Br&#x00F6;der et al., 2018</xref>; <xref ref-type="bibr" rid="B48">Grotheer et al., 2020</xref>). Furthermore, due to competition with marine sulfate reduction, most likely no CH<sub>4</sub> would be produced in the marine surface sediments (<xref ref-type="bibr" rid="B71">Knoblauch et al., 2018</xref>).</p>
</sec>
<sec id="S4.SS6">
<title>CO<sub>2</sub> Release Dynamics Along the Yukon Coast</title>
<p>The erosion type and coastal morphology may strongly influence the GHG release potential along vulnerable permafrost coastlines. Our main study area, Qikiqtaruk &#x2013; Herschel Island, is dominated by high cliffs (mean elevation &#x223C;25 m) and retrogressive thaw slumps, which together affect &#x223C;7% of the coast (<xref ref-type="fig" rid="F1">Figures 1</xref>, <xref ref-type="fig" rid="F2">2</xref>, <xref ref-type="bibr" rid="B81">Lantuit and Pollard, 2008</xref>; <xref ref-type="bibr" rid="B106">Ramage et al., 2017</xref>). Thermoabrasion of the cliff tops and headwall retreat in thaw slumps may result in an initial CO<sub>2</sub> pulse <italic>onshore</italic> with up to &#x223C;4% of OC mineralized into CO<sub>2</sub> within one season (<xref ref-type="bibr" rid="B130">Tanski et al., 2019</xref>). Longer transport pathways of exposed organic matter along the sloping cliff faces or within thaw slump systems (<xref ref-type="fig" rid="F1">Figures 1A,B</xref>) then result in a <italic>delayed</italic> release into the sea with further OC mineralization (&#x223C;5% OC loss as CO<sub>2</sub> measured during one warm season) at low rates (mimicked by <italic>mud debris</italic> incubations in this study) taking place in the subsequent warm seasons assuming the material discharges into the sea in the following years or even later. This adds to the initial permafrost CO<sub>2</sub> pulse <italic>onshore</italic> before release into the <italic>nearshore</italic> zone (<xref ref-type="fig" rid="F5">Figure 5</xref>). Within thaw slump systems, eroded sediments can reside on long time scales <italic>onshore</italic> (years to decades) before release into the sea (<xref ref-type="bibr" rid="B29">Cray and Pollard, 2015</xref>). This long transit time can result in a substantial OC loss (up to &#x223C;50%) with portions mineralized into CO<sub>2</sub> or CH<sub>4</sub> (<xref ref-type="bibr" rid="B2">Abbott et al., 2015</xref>; <xref ref-type="bibr" rid="B129">Tanski et al., 2017</xref>, <xref ref-type="bibr" rid="B130">2019</xref>). Similarly, eroded debris can further accumulate on the beach for longer time spans (potentially exceeding one warm season) before being washed into the sea during storm surges or high tides (<xref ref-type="bibr" rid="B98">Obu et al., 2015</xref>; <xref ref-type="bibr" rid="B30">Cunliffe et al., 2019</xref>). This transition stage could further promote reworking of OC and direct CO<sub>2</sub> release to the atmosphere <italic>onshore</italic>. Photo-oxidation processes may have further increased degradation and CO<sub>2</sub> production during transit from land to sea (<xref ref-type="bibr" rid="B26">Cory et al., 2013</xref>; <xref ref-type="bibr" rid="B137">Ward and Cory, 2016</xref>).</p>
<fig id="F5" position="float">
<label>FIGURE 5</label>
<caption><p>Infographic summarizing potential organic carbon loss (%OC as CO<sub>2</sub>) during coastal erosion processes from different erosion types in an Arctic warm season and entire year upon erosion in the sea. The magnitude of absolute carbon dioxide (mg CO<sub>2</sub> gdw) release is indicated by the size of yellow bubbles. Release of <italic>mud debris</italic> (gray flow) from thaw slumps or other thaw features into the <italic>nearshore</italic> is likely delayed with longer residence times <italic>onshore</italic>, resulting in a steady CO<sub>2</sub> release at low rates complementing CO<sub>2</sub> pulses during initial permafrost thaw and erosion. <italic>Cliff debris</italic> (brown flow) along low bluffs is likely to be transported more directly into the <italic>nearshore</italic>, resulting only in a short-term CO<sub>2</sub> pulse and overall low OC loss during transit (<xref ref-type="fig" rid="F1">Figure 1</xref>). After erosion into the <italic>nearshore</italic> CO<sub>2</sub> is produced, which can be amplified by seawater, in particular for <italic>cliff debris</italic> and <italic>in situ</italic> permafrost where transport time is short. Carbon losses were modeled for the Arctic open-water season (&#x223C;four months) and the entire year based on short term (&#x223C;two months) incubation experiments at 4&#x00B0;C under dark and aerobic conditions. Carbon loss rates from permafrost erosion are taken from <xref ref-type="bibr" rid="B130">Tanski et al. (2019)</xref> and displayed as reference for <italic>in situ</italic> permafrost (&#x223C;four month incubation at same conditions). The asterisk (&#x002A;) indicates that once eroded into the sea OC degradation takes place during the entire year and is not limited to the warm seasons. Burial estimates are taken from <xref ref-type="bibr" rid="B28">Couture et al. (2018)</xref> and <xref ref-type="bibr" rid="B48">Grotheer et al. (2020)</xref>.</p></caption>
<graphic xlink:href="feart-09-630493-g005.tif"/>
</fig>
<p>In contrast, gully channels that intersect high bluffs, and thaw streams that drain slump systems (<xref ref-type="fig" rid="F1">Figures 1A,B</xref>) may transport eroded permafrost OC more quickly and on a <italic>direct</italic> pathway towards the sea, potentially diminishing CO<sub>2</sub> release <italic>onshore</italic>. This <italic>direct</italic> pathway likely also applies to coastal stretches with low cliffs, which can be found especially on the southeast side of Qikiqtaruk &#x2013; Herschel Island, which we tried to mimic with the <italic>cliff debris</italic> incubations. Along these cliffs (<xref ref-type="fig" rid="F2">Figures 2</xref>, <xref ref-type="fig" rid="F5">5</xref>), approximately 3% of OC can be mineralized into CO<sub>2</sub> within one warm season during transit <italic>onshore</italic>. The debris along low cliffs is likely removed quickly within one season with only larger collapsing permafrost blocks remaining for a longer period <italic>onshore</italic> on the beach (season to years). Correspondingly, the initial CO<sub>2</sub> pulse is likely complemented by continuing CO<sub>2</sub> production at lower rates. For this study we assumed aerated conditions during transport. Yet, when eroded material gets redeposited in mud pools or lobes <italic>onshore</italic>, CH<sub>4</sub> production may replace CO<sub>2</sub> production if water-logged and oxygen-depleted conditions apply (<xref ref-type="bibr" rid="B72">Knoblauch et al., 2013</xref>; <xref ref-type="bibr" rid="B112">Sch&#x00E4;del et al., 2016</xref>).</p>
<p>Upon release into the <italic>nearshore</italic> waters, OC is likely further mineralized within erosion plumes or deposited sediments. Seawater may further promote OC mineralization (<xref ref-type="fig" rid="F5">Figure 5</xref>), especially if transport is <italic>direct</italic> (in the case of collapsed permafrost or cliff debris) and if the water column is oxygen-saturated. Seawater enhances the CO<sub>2</sub> production from <italic>cliff debris</italic> with corresponding OC losses increasing from 1.6 &#x00B1; 0.3 to 2.2 &#x00B1; 0.2% after incubation with seawater mimicking <italic>nearshore</italic> conditions (<xref ref-type="table" rid="T2">Table 2</xref>). Enhanced OC loss was also observed for <italic>in situ</italic> permafrost mixed with seawater with TOC losses increasing from 1.1 &#x00B1; 0.0 to 1.5 &#x00B1; 0.2% in organic-rich permafrost and from 3.9 &#x00B1; 0.2 to 6.2 &#x00B1; 1.2% in mineral permafrost (<xref ref-type="bibr" rid="B130">Tanski et al., 2019</xref>). If transport to the <italic>nearshore</italic> is <italic>delayed</italic>, OC transferred to the sea probably continues to degrade at the same relatively low rates as <italic>onshore</italic> with OC losses of &#x223C;5% within a warm season of four months (<xref ref-type="fig" rid="F5">Figure 5</xref>). Yet, for both scenarios organic matter degradation in <italic>nearshore</italic> sediments likely takes place during the entire year and is not limited only to the warm season since <italic>nearshore</italic> sediments do not freeze up during the cold season. Once eroded into the <italic>nearshore</italic>, the total OC loss as CO<sub>2</sub>-C from <italic>mud debris</italic> and <italic>cliff debris</italic> could be &#x223C;7&#x2013;11% after one year (<xref ref-type="fig" rid="F5">Figure 5</xref>). Depending on the depositional environment, OC can be either buried on the shelf or transported towards the continental slope on up to millennial time scales (<xref ref-type="bibr" rid="B94">Naidu et al., 2000</xref>; <xref ref-type="bibr" rid="B45">Go&#x00F1;i et al., 2013</xref>; <xref ref-type="bibr" rid="B16">Br&#x00F6;der et al., 2018</xref>). Locally, large portions of eroded OC (&#x223C;12 to 40%) are stored in <italic>nearshore</italic> sediments and local depressions on the shelf such as Herschel Basin (<xref ref-type="bibr" rid="B28">Couture et al., 2018</xref>; <xref ref-type="bibr" rid="B48">Grotheer et al., 2020</xref>). On the seafloor, effective aerobic degradation likely only takes place in the upper few millimeters of the sediment column and at the water-sediment boundary, where microbial communities allow for higher respiration rates (<xref ref-type="bibr" rid="B108">Rasmussen and Jorgensen, 1992</xref>; <xref ref-type="bibr" rid="B7">Arndt et al., 2013</xref>; <xref ref-type="bibr" rid="B17">Br&#x00FC;chert et al., 2018</xref>). Bioturbation, currents and ice scouring may facilitate resuspension and therefore oxygen resupply and CO<sub>2</sub> production in deeper sediment columns eventually (<xref ref-type="bibr" rid="B54">H&#x00E9;quette et al., 1995</xref>; <xref ref-type="bibr" rid="B7">Arndt et al., 2013</xref>). Under anaerobic conditions microbial communities that can produce CH<sub>4</sub> can establish after years and substantial amounts of CH<sub>4</sub> being produced and released either directly as CH<sub>4</sub> or oxidized as CO<sub>2</sub> from the seafloor (<xref ref-type="bibr" rid="B99">Overduin et al., 2015</xref>; <xref ref-type="bibr" rid="B71">Knoblauch et al., 2018</xref>). Although further GHG production of eroded material is very likely in the <italic>nearshore</italic>, it is unclear if or from which water depth produced CO<sub>2</sub> evades to the atmosphere. Outgassing of degradation-derived CO<sub>2</sub> or CH<sub>4</sub> from oversaturated water layers, however, can occur locally and is promoted by resuspension, storms or upwelling events (<xref ref-type="bibr" rid="B90">Mathis et al., 2012</xref>; <xref ref-type="bibr" rid="B133">Vonk et al., 2012</xref>; <xref ref-type="bibr" rid="B117">Semiletov et al., 2016</xref>; <xref ref-type="bibr" rid="B102">Pipko et al., 2017</xref>).</p>
<p>Along the adjacent Yukon mainland coast approximately one third of the entire coastline is characterized by actively eroding cliffs (of variable elevation), with the remainder being gently sloping tundra (&#x223C;17%) and inundated coastlines (&#x223C;11%) as well as beach and gravel spits (<xref ref-type="bibr" rid="B61">Irrgang et al., 2018</xref>). A <italic>delayed</italic> release similar to the high cliffs on Qikiqtaruk &#x2013; Herschel Island may apply to the actively eroding cliffs in the formerly glaciated part of the Yukon coast towards the Mackenzie Delta. Here, cliffs are high (mean elevation of up to &#x223C;30m) and thaw slumps are ubiquitous (up to &#x223C;16% of the coastline) promoting substantial OC turnover <italic>onshore</italic> before release into the ocean (<xref ref-type="bibr" rid="B27">Couture and Pollard, 2015</xref>; <xref ref-type="bibr" rid="B106">Ramage et al., 2017</xref>). In the formerly unglaciated part towards the Alaskan border (<xref ref-type="fig" rid="F1">Figures 1C,D</xref>), cliffs are much lower (&#x223C;6.5 m mean elevation) and residence times of eroded OC <italic>onshore</italic> likely to be very short (weeks to years) due to the particularly high erosion rates in this region (&#x223C;1.4 m yr<sup>&#x2013;1</sup>), which results in a shorter time span for OC mineralization during erosion (<xref ref-type="bibr" rid="B27">Couture and Pollard, 2015</xref>; <xref ref-type="bibr" rid="B61">Irrgang et al., 2018</xref>). Along coastal parts where tundra is sloping towards the beach and thereby restricting exposure of permafrost, OC loss might be even lower and the cycling of released OC may primarily take place in the seawater column or upon deposition in <italic>nearshore</italic> sediments. In turn, inundation and potential permafrost degradation could promote OC mineralization <italic>onshore</italic> and release substantial amounts of CO<sub>2</sub> before transport into the ocean (<xref ref-type="bibr" rid="B130">Tanski et al., 2019</xref>). At present, how much OC is converted into CO<sub>2</sub> along the different coastal types is highly speculative. Yet, it is likely that the response of OC to erosion and the magnitude of CO<sub>2</sub> release varies between coastal and erosion types. Based on the annual TOC flux from land to sea of 36 Gg yr<sup>&#x2013;1</sup> for the Yukon coast (<xref ref-type="bibr" rid="B28">Couture et al., 2018</xref>), we would estimate that up to 1.8 Gg CO<sub>2</sub> yr<sup>&#x2013;1</sup> could be released as CO<sub>2</sub> during the erosion process onshore assuming an OC loss of up to &#x223C;5% during the warm season and up to 3.9 Gg CO<sub>2</sub> yr<sup>&#x2013;1</sup> from <italic>nearshore</italic> sediments assuming an OC loss of &#x223C;11% for an entire year since eroded sediments on the seafloor do not freeze anymore (<xref ref-type="fig" rid="F5">Figure 5</xref>). Local dynamic environmental conditions (e.g., higher air temperatures and sunlight exposure) and processes (e.g., drying and rewetting of debris in the coastal zone) may increase OC degradation.</p>
</sec>
</sec>
<sec id="S5">
<title>Conclusion</title>
<p>Coastal morphology and erosion type play a substantial role in determining the greenhouse gas release potential during erosion along permafrost coasts in the Arctic. <italic>Mud debris</italic> and <italic>cliff debris</italic> from an outflow of a thaw slump system and a low collapsing bluff, respectively, representing different coastal erosion scenarios released substantial amounts of CO<sub>2</sub> (1.4 &#x00B1; 0.1 to 4.0 &#x00B1; 0.9 mg CO<sub>2</sub> gdw<sup>&#x2013;1</sup>) over a short period (&#x223C;two months) corresponding to an initial OC loss &#x223C;1.6&#x2013;2.6%. The relatively fresh and OC-rich <italic>cliff debris</italic> resulted in a &#x223C;four times higher CO<sub>2</sub> release than for <italic>mud debris</italic>. Yet, when normalized to OC content, CO<sub>2</sub> release was &#x223C;three times higher from <italic>mud debris</italic> indicating higher biodegradability of the older and more mineral OC. CO<sub>2</sub> release was particularly high with addition of seawater, indicating potential priming effects in the coastal realm. Upon release into the ocean, only a small portion of OC initially enters the seawater DOC pool. Our results suggest that high bluffs or coasts with presence of thermoerosional features are characterized by a <italic>delayed</italic> release that consists of an initial CO<sub>2</sub> pulse from permafrost erosion followed by a subsequent CO<sub>2</sub> release at lower rates in <italic>mud debris</italic>, promoting OC degradation during protracted transit from land to sea in the warm season. In contrast, erosion of <italic>cliff debris</italic> along low bluffs that may contain proportionally more OC results only in a short-term CO<sub>2</sub> pulse with OC quickly removed by waves. In the <italic>nearshore</italic> zone, CO<sub>2</sub> production from eroded sediments continues provided oxygen is available, likely taking place the entire year. After the duration of an Arctic warms season (&#x223C;four month) OC losses of up &#x223C;5% were modeled and after one year, up to &#x223C;11% of OC could be decomposed and released as CO<sub>2</sub> once eroded sediments are deposited in the <italic>nearshore</italic>. The magnitude of CO<sub>2</sub> release may be underestimated when using traditional incubation experiments since coastal environmental conditions are difficult to account for yet likely enhance degradation. More sophisticated incubation set-ups that mimic changing environmental and site-specific variables, or continuous GHG measurement systems <italic>onshore</italic> (e.g., eddy covariance towers) and in the <italic>nearshore</italic> (e.g., pop-up buoys with <italic>in situ p</italic>CO<sub>2</sub> sensors), accounting for seasonal fluctuations and uptake processes from vegetation and phytoplankton, would be needed to derive the actual GHG release signal along eroding permafrost coasts in different Arctic regions.</p>
</sec>
<sec id="S6">
<title>Data Availability Statement</title>
<p>The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.</p>
</sec>
<sec id="S7">
<title>Author Contributions</title>
<p>GT, HL, DW, JV, and LB created the study design and incubation set-up. GT, DW, and TS carried out the gas concentration measurements. CK and GT recalculated gas concentration and estimated TOC losses. CB calibrated and applied the dynamic carbon decomposition model. GT and LB carried out the extraction of lipid biomarkers. TT measured lipid biomarkers. LB, JV, GT, and TT processed and interpreted the data. HL, MF, and JS supported the bulk geochemical and stable carbon isotope analysis and data interpretation. BK measured and evaluated DOC concentrations. LB, NH, and TE carried out radiocarbon analysis and data analysis. GT wrote the manuscript with contributions from all co-authors. All authors contributed to the article and approved the submitted version.</p>
</sec>
<sec sec-type="COI-statement" id="conf1">
<title>Conflict of Interest</title>
<p>The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.</p>
</sec>
</body>
<back>
<fn-group>
<fn fn-type="financial-disclosure">
<p><bold>Funding.</bold> We acknowledge and are grateful for the financial support from the H2020 project NUNATARYUK (grant 773421), the Helmholtz young investigators group TEAM (grant VH-NG-821 to TS) and the ERC StG project THAWSOME (grant 676982 to JV). JS was supported by the Changing Arctic Ocean program (NERC-BMBF project CACOON, grant 03F0806A) and CB by the German research foundation DFG (BE 6485/1-1).</p>
</fn>
</fn-group>
<ack>
<p>We would like to thank O. Burckhardt, J. Oury, C. Burau, D. Scheidemann, H. Meyer, M. Weiner, K. Keskitalo, and D. Jong for support during lab work. K. Klein and D. Jong are thanked for assistance during field work and J. Kahl for logistical support. We thank A. Irrgang for contributing photographs from field work. We would like to especially thank the park rangers and R. Gordon from Qikiqtaruk &#x2013; Herschel Island Territorial Park for their support and guidance on their land. The Aurora Research Institute in Inuvik is thanked for the logistical support on site. Data supporting this study is available on the PANGAEA data repository (in review; data submitted on 05 January 2021).</p>
</ack>
<sec id="S10" sec-type="supplementary material">
<title>Supplementary Material</title>
<p>The Supplementary Material for this article can be found online at: <ext-link ext-link-type="uri" xlink:href="https://www.frontiersin.org/articles/10.3389/feart.2021.630493/full#supplementary-material">https://www.frontiersin.org/articles/10.3389/feart.2021.630493/full#supplementary-material</ext-link></p>
<supplementary-material xlink:href="Data_Sheet_1.pdf" id="FS1" mimetype="application/pdf" xmlns:xlink="http://www.w3.org/1999/xlink"/>
</sec>
<ref-list>
<title>References</title>
<ref id="B1"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Abbott</surname> <given-names>B. W.</given-names></name> <name><surname>Jones</surname> <given-names>J. B.</given-names></name></person-group> (<year>2015</year>). <article-title>Permafrost collapse alters soil carbon stocks, respiration, CH4, and N2O in upland tundra.</article-title> <source><italic>Glob. Change Biol.</italic></source> <volume>21</volume> <fpage>4570</fpage>&#x2013;<lpage>4587</lpage>. <pub-id pub-id-type="doi">10.1111/gcb.13069</pub-id> <pub-id pub-id-type="pmid">26301544</pub-id></citation></ref>
<ref id="B2"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Abbott</surname> <given-names>B. W.</given-names></name> <name><surname>Jones</surname> <given-names>J. B.</given-names></name> <name><surname>Godsey</surname> <given-names>S. E.</given-names></name> <name><surname>Larouche</surname> <given-names>J. R.</given-names></name> <name><surname>Bowden</surname> <given-names>W. B.</given-names></name></person-group> (<year>2015</year>). <article-title>Patterns and persistence of hydrologic carbon and nutrient export from collapsing upland permafrost.</article-title> <source><italic>Biogeosciences</italic></source> <volume>12</volume> <fpage>3725</fpage>&#x2013;<lpage>3740</lpage>. <pub-id pub-id-type="doi">10.5194/bg-12-3725-2015</pub-id></citation></ref>
<ref id="B3"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Abbott</surname> <given-names>B. W.</given-names></name> <name><surname>Larouche</surname> <given-names>J. R.</given-names></name> <name><surname>Jones</surname> <given-names>J. B.</given-names></name> <name><surname>Bowden</surname> <given-names>W. B.</given-names></name> <name><surname>Balser</surname> <given-names>A. W.</given-names></name></person-group> (<year>2014</year>). <article-title>Elevated dissolved organic carbon biodegradability from thawing and collapsing permafrost.</article-title> <source><italic>J. Geophys. Res. Biogeosci.</italic></source> <volume>119</volume> <fpage>2049</fpage>&#x2013;<lpage>2063</lpage>. <pub-id pub-id-type="doi">10.1002/2014JG002678</pub-id></citation></ref>
<ref id="B4"><citation citation-type="journal"><collab>AMAP</collab> (<year>2017</year>). <source><italic>Snow, Water, Ice and Permafrost in the Arctic (SWIPA) 2017.</italic></source> <publisher-loc>Oslo</publisher-loc>: <publisher-name>Arctic Monitoring and Assessment Programme</publisher-name>.</citation></ref>
<ref id="B5"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Andr&#x00E9;n</surname> <given-names>O.</given-names></name> <name><surname>K&#x00E4;tterer</surname> <given-names>T.</given-names></name></person-group> (<year>1997</year>). <article-title>ICBM: the introductory carbon balance model for exploration of soil carbon balances.</article-title> <source><italic>Ecol. Appl.</italic></source> <volume>7</volume> <fpage>1226</fpage>&#x2013;<lpage>1236</lpage>. <pub-id pub-id-type="doi">10.1890/1051-07611997007[1226:ITICBM]2.0.CO;2</pub-id></citation></ref>
<ref id="B6"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Are</surname> <given-names>F. E.</given-names></name> <name><surname>Reimnitz</surname> <given-names>E.</given-names></name> <name><surname>Grigoriev</surname> <given-names>M. N.</given-names></name> <name><surname>Hubberten</surname> <given-names>H. W.</given-names></name> <name><surname>Rachold</surname> <given-names>V.</given-names></name></person-group> (<year>2008</year>). <article-title>The influence of cryogenic processes on the erosional arctic shoreface.</article-title> <source><italic>J. Coast. Res.</italic></source> <volume>241</volume> <fpage>110</fpage>&#x2013;<lpage>121</lpage>. <pub-id pub-id-type="doi">10.2112/05-0573.1</pub-id></citation></ref>
<ref id="B7"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Arndt</surname> <given-names>S.</given-names></name> <name><surname>J&#x00F8;rgensen</surname> <given-names>B. B.</given-names></name> <name><surname>LaRowe</surname> <given-names>D. E.</given-names></name> <name><surname>Middelburg</surname> <given-names>J. J.</given-names></name> <name><surname>Pancost</surname> <given-names>R. D.</given-names></name> <name><surname>Regnier</surname> <given-names>P.</given-names></name></person-group> (<year>2013</year>). <article-title>Quantifying the degradation of organic matter in marine sediments: a review and synthesis.</article-title> <source><italic>Earth Sci. Rev.</italic></source> <volume>123</volume> <fpage>53</fpage>&#x2013;<lpage>86</lpage>. <pub-id pub-id-type="doi">10.1016/j.earscirev.2013.02.008</pub-id></citation></ref>
<ref id="B8"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Barnhart</surname> <given-names>K. R.</given-names></name> <name><surname>Anderson</surname> <given-names>R. S.</given-names></name> <name><surname>Overeem</surname> <given-names>I.</given-names></name> <name><surname>Wobus</surname> <given-names>C.</given-names></name> <name><surname>Clow</surname> <given-names>G. D.</given-names></name> <name><surname>Urban</surname> <given-names>F. E.</given-names></name></person-group> (<year>2014</year>). <article-title>Modeling erosion of ice-rich permafrost bluffs along the Alaskan Beaufort Sea coast.</article-title> <source><italic>J. Geophys. Res. Earth Surf.</italic></source> <volume>119</volume> <fpage>1155</fpage>&#x2013;<lpage>1179</lpage>. <pub-id pub-id-type="doi">10.1002/2013JF002845</pub-id></citation></ref>
<ref id="B9"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Battin</surname> <given-names>T. J.</given-names></name> <name><surname>Kaplan</surname> <given-names>L. A.</given-names></name> <name><surname>Findlay</surname> <given-names>S.</given-names></name> <name><surname>Hopkinson</surname> <given-names>C. S.</given-names></name> <name><surname>Marti</surname> <given-names>E.</given-names></name> <name><surname>Packman</surname> <given-names>A. I.</given-names></name></person-group> (<year>2008</year>). <article-title>Biophysical controls on organic carbon fluxes in fluvial networks.</article-title> <source><italic>Nat. Geosci.</italic></source> <volume>1</volume> <fpage>95</fpage>&#x2013;<lpage>100</lpage>. <pub-id pub-id-type="doi">10.1038/ngeo101</pub-id></citation></ref>
<ref id="B10"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Bendixen</surname> <given-names>M.</given-names></name> <name><surname>Iversen</surname> <given-names>L. L.</given-names></name> <name><surname>Bj&#x00F8;rk</surname> <given-names>A. A.</given-names></name> <name><surname>Elberling</surname> <given-names>B.</given-names></name> <name><surname>Westergaard-Nielsen</surname> <given-names>A.</given-names></name> <name><surname>Overeem</surname> <given-names>I.</given-names></name><etal/></person-group> (<year>2017</year>). <article-title>Delta progradation in Greenland driven by increasing glacial mass loss.</article-title> <source><italic>Nature</italic></source> <volume>550</volume> <fpage>101</fpage>&#x2013;<lpage>104</lpage>. <pub-id pub-id-type="doi">10.1038/nature23873</pub-id> <pub-id pub-id-type="pmid">28980627</pub-id></citation></ref>
<ref id="B11"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Bianchi</surname> <given-names>T. S.</given-names></name></person-group> (<year>2011</year>). <article-title>The role of terrestrially derived organic carbon in the coastal ocean: a changing paradigm and the priming effect.</article-title> <source><italic>Proc. Natl. Acad. Sci. U.S.A.</italic></source> <volume>108</volume> <fpage>19473</fpage>&#x2013;<lpage>19481</lpage>. <pub-id pub-id-type="doi">10.1073/pnas.1017982108</pub-id> <pub-id pub-id-type="pmid">22106254</pub-id></citation></ref>
<ref id="B12"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Biskaborn</surname> <given-names>B. K.</given-names></name> <name><surname>Smith</surname> <given-names>S. S.</given-names></name> <name><surname>Noetzli</surname> <given-names>J.</given-names></name> <name><surname>Matthes</surname> <given-names>H.</given-names></name> <name><surname>Vieira</surname> <given-names>G.</given-names></name> <name><surname>Streletskiy</surname> <given-names>D. A.</given-names></name><etal/></person-group> (<year>2019</year>). <article-title>Permafrost is warming at a global scale.</article-title> <source><italic>Nat. Commun.</italic></source> <volume>10</volume>:<issue>264</issue>. <pub-id pub-id-type="doi">10.1038/s41467-018-08240-4</pub-id> <pub-id pub-id-type="pmid">30651568</pub-id></citation></ref>
<ref id="B13"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Blair</surname> <given-names>N.</given-names></name> <name><surname>Aller</surname> <given-names>R.</given-names></name></person-group> (<year>2012</year>). <article-title>The fate of terrestrial organic carbon in the marine environment.</article-title> <source><italic>Annu. Rev. Mar. Sci.</italic></source> <volume>4</volume> <fpage>401</fpage>&#x2013;<lpage>423</lpage>. <pub-id pub-id-type="doi">10.1146/annurev-marine-120709-142717</pub-id> <pub-id pub-id-type="pmid">22457981</pub-id></citation></ref>
<ref id="B14"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Blasco</surname> <given-names>S. M.</given-names></name> <name><surname>Fortin</surname> <given-names>G.</given-names></name> <name><surname>Hill</surname> <given-names>P. R.</given-names></name> <name><surname>O&#x2019;Connor</surname> <given-names>M. J.</given-names></name> <name><surname>Brigham-Grette</surname> <given-names>J. K.</given-names></name></person-group> (<year>1990</year>). &#x201C;<article-title>The late neogene and quaternary stratigraphy of the Canadian Beaufort continental shelf</article-title>,&#x201D; in <source><italic>The Arctic Ocean Region</italic></source>, <role>eds</role> <person-group person-group-type="editor"><name><surname>Grantz</surname> <given-names>A.</given-names></name> <name><surname>Johnson</surname> <given-names>L.</given-names></name> <name><surname>Sweeney</surname> <given-names>J. F.</given-names></name></person-group> (<publisher-loc>Boulder, CO</publisher-loc>: <publisher-name>Geological Society of America</publisher-name>), <fpage>491</fpage>&#x2013;<lpage>502</lpage>.</citation></ref>
<ref id="B15"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Bray</surname> <given-names>E. E.</given-names></name> <name><surname>Evans</surname> <given-names>E. D.</given-names></name></person-group> (<year>1961</year>). <article-title>Distribution of n-paraffins as a clue to recognition of source beds.</article-title> <source><italic>Geochim. Cosmochim. Acta</italic></source> <volume>22</volume> <fpage>2</fpage>&#x2013;<lpage>15</lpage>. <pub-id pub-id-type="doi">10.1016/0016-7037(61)90069-2</pub-id></citation></ref>
<ref id="B16"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Br&#x00F6;der</surname> <given-names>L.</given-names></name> <name><surname>Tesi</surname> <given-names>T.</given-names></name> <name><surname>Andersson</surname> <given-names>A.</given-names></name> <name><surname>Semiletov</surname> <given-names>I.</given-names></name> <name><surname>Gustafsson</surname> <given-names>&#x00D6;</given-names></name></person-group> (<year>2018</year>). <article-title>Bounding cross-shelf transport time and degradation in Siberian-Arctic land-ocean carbon transfer.</article-title> <source><italic>Nat. Commun.</italic></source> <volume>9</volume>:<issue>806</issue>. <pub-id pub-id-type="doi">10.1038/s41467-018-03192-1</pub-id> <pub-id pub-id-type="pmid">29476050</pub-id></citation></ref>
<ref id="B17"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Br&#x00FC;chert</surname> <given-names>V.</given-names></name> <name><surname>Br&#x00F6;der</surname> <given-names>L.</given-names></name> <name><surname>Sawicka</surname> <given-names>J. E.</given-names></name> <name><surname>Tesi</surname> <given-names>T.</given-names></name> <name><surname>Joye</surname> <given-names>S. P.</given-names></name> <name><surname>Sun</surname> <given-names>X.</given-names></name><etal/></person-group> (<year>2018</year>). <article-title>Carbon mineralization in Laptev and East Siberian sea shelf and slope sediment.</article-title> <source><italic>Biogeosciences</italic></source> <volume>15</volume> <fpage>471</fpage>&#x2013;<lpage>490</lpage>. <pub-id pub-id-type="doi">10.5194/bg-15-471-2018</pub-id></citation></ref>
<ref id="B18"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Brunauer</surname> <given-names>S.</given-names></name> <name><surname>Emmett</surname> <given-names>P. H.</given-names></name> <name><surname>Teller</surname> <given-names>E.</given-names></name></person-group> (<year>1938</year>). <article-title>Adsorption of gases in multimolecular layers.</article-title> <source><italic>J. Am. Chem. Soc.</italic></source> <volume>60</volume> <fpage>309</fpage>&#x2013;<lpage>319</lpage>. <pub-id pub-id-type="doi">10.1021/ja01269a023</pub-id></citation></ref>
<ref id="B19"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Burn</surname> <given-names>C. R.</given-names></name></person-group> (<year>1997</year>). <article-title>Cryostratigraphy, paleogeography, and climate change during the early Holocene warm interval, western Arctic coast, Canada.</article-title> <source><italic>Can. J. Earth Sci.</italic></source> <volume>34</volume> <fpage>912</fpage>&#x2013;<lpage>925</lpage>. <pub-id pub-id-type="doi">10.1139/e17-076</pub-id></citation></ref>
<ref id="B20"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Burn</surname> <given-names>C. R.</given-names></name></person-group> (<year>2012</year>). <source><italic>Herschel Island Qikiqtaryuk - A Natural and Cultural History of Yukon&#x2019;s Arctic Island.</italic></source> <publisher-loc>Calgary</publisher-loc>: <publisher-name>University of Calgary Press</publisher-name>.</citation></ref>
<ref id="B21"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Burn</surname> <given-names>C. R.</given-names></name> <name><surname>Zhang</surname> <given-names>Y.</given-names></name></person-group> (<year>2009</year>). <article-title>Permafrost and climate change at Herschel Island (Qikiqtaruq), Yukon Territory, Canada.</article-title> <source><italic>J. Geophys. Res. Earth Surf.</italic></source> <volume>114</volume> <fpage>1</fpage>&#x2013;<lpage>16</lpage>. <pub-id pub-id-type="doi">10.1029/2008JF001087</pub-id></citation></ref>
<ref id="B22"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Chen</surname> <given-names>L.</given-names></name> <name><surname>Liu</surname> <given-names>L.</given-names></name> <name><surname>Mao</surname> <given-names>C.</given-names></name> <name><surname>Qin</surname> <given-names>S.</given-names></name> <name><surname>Wang</surname> <given-names>J.</given-names></name> <name><surname>Liu</surname> <given-names>F.</given-names></name><etal/></person-group> (<year>2018</year>). <article-title>Nitrogen availability regulates topsoil carbon dynamics after permafrost thaw by altering microbial metabolic efficiency.</article-title> <source><italic>Nat. Commun.</italic></source> <volume>9</volume>:<issue>3951</issue>. <pub-id pub-id-type="doi">10.1038/s41467-018-06232-y</pub-id> <pub-id pub-id-type="pmid">30262803</pub-id></citation></ref>
<ref id="B23"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Chen</surname> <given-names>X.</given-names></name> <name><surname>Liu</surname> <given-names>X.</given-names></name> <name><surname>Wei</surname> <given-names>Y.</given-names></name> <name><surname>Huang</surname> <given-names>Y.</given-names></name></person-group> (<year>2019</year>). <article-title>Production of long-chain n-alkyl lipids by heterotrophic microbes: new evidence from Antarctic lakes.</article-title> <source><italic>Organ. Geochem.</italic></source> <volume>138</volume>:<issue>103909</issue>. <pub-id pub-id-type="doi">10.1016/j.orggeochem.2019.103909</pub-id></citation></ref>
<ref id="B24"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Ciais</surname> <given-names>P.</given-names></name> <name><surname>Sabine</surname> <given-names>C.</given-names></name> <name><surname>Bala</surname> <given-names>G.</given-names></name> <name><surname>Bopp</surname> <given-names>L.</given-names></name> <name><surname>Brovkin</surname> <given-names>V.</given-names></name> <name><surname>Canadell</surname> <given-names>J., et al.</given-names></name></person-group> (<role>eds</role>) (<year>2013</year>). &#x201C;<article-title>Carbon and other biogeochemical cycles</article-title>,&#x201D; in <source><italic>Climate Change 2013: The Physical Science Basis. Contribution of Working Group 1 to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change</italic></source>, <role>eds</role> <person-group person-group-type="editor"><name><surname>Stocker</surname> <given-names>T. F.</given-names></name> <name><surname>Qin</surname> <given-names>D.</given-names></name> <name><surname>Plattner</surname> <given-names>G. K.</given-names></name> <name><surname>Tignor</surname> <given-names>M.</given-names></name> <name><surname>Allen</surname> <given-names>S. K.</given-names></name> <name><surname>Boschung</surname> <given-names>J.</given-names></name><etal/></person-group> (<publisher-loc>Cambridge</publisher-loc>: <publisher-name>Cambridge University Press</publisher-name>).</citation></ref>
<ref id="B25"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Coch</surname> <given-names>C.</given-names></name> <name><surname>Lamoureux</surname> <given-names>S. F.</given-names></name> <name><surname>Knoblauch</surname> <given-names>C.</given-names></name> <name><surname>Eischeid</surname> <given-names>I.</given-names></name> <name><surname>Fritz</surname> <given-names>M.</given-names></name> <name><surname>Obu</surname> <given-names>J.</given-names></name><etal/></person-group> (<year>2018</year>). <article-title>Summer rainfall dissolved organic carbon, solute, and sediment fluxes in a small Arctic coastal catchment on Herschel Island (Yukon Territory, Canada).</article-title> <source><italic>Arct. Sci.</italic></source> <volume>4</volume> <fpage>750</fpage>&#x2013;<lpage>780</lpage>. <pub-id pub-id-type="doi">10.1139/as-2018-0010</pub-id></citation></ref>
<ref id="B26"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Cory</surname> <given-names>R. M.</given-names></name> <name><surname>Crump</surname> <given-names>B. C.</given-names></name> <name><surname>Dobkowski</surname> <given-names>J. A.</given-names></name> <name><surname>Kling</surname> <given-names>G. W.</given-names></name></person-group> (<year>2013</year>). <article-title>Surface exposure to sunlight stimulates CO2 release from permafrost soil carbon in the Arctic.</article-title> <source><italic>Proc. Natl. Acad. Sci. U.S.A.</italic></source> <volume>110</volume> <fpage>3429</fpage>&#x2013;<lpage>3434</lpage>. <pub-id pub-id-type="doi">10.1073/pnas.1214104110</pub-id> <pub-id pub-id-type="pmid">23401500</pub-id></citation></ref>
<ref id="B27"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Couture</surname> <given-names>N.</given-names></name> <name><surname>Pollard</surname> <given-names>W. H.</given-names></name></person-group> (<year>2015</year>). &#x201C;<article-title>Ground ice determinations along the Yukon coast using a morphological model</article-title>,&#x201D; in <source><italic>Proceedings, GeoQuebec 2015, 7th Canadian Permafrost Conference</italic></source>, (<publisher-loc>Qu&#x00E9;bec</publisher-loc>).</citation></ref>
<ref id="B28"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Couture</surname> <given-names>N. J.</given-names></name> <name><surname>Irrgang</surname> <given-names>A.</given-names></name> <name><surname>Pollard</surname> <given-names>W.</given-names></name> <name><surname>Lantuit</surname> <given-names>H.</given-names></name> <name><surname>Fritz</surname> <given-names>M.</given-names></name></person-group> (<year>2018</year>). <article-title>Coastal erosion of permafrost soils along the Yukon coastal plain and fluxes of organic carbon to the Canadian Beaufort Sea.</article-title> <source><italic>J. Geophys. Res. Biogeosci.</italic></source> <volume>123</volume> <fpage>406</fpage>&#x2013;<lpage>422</lpage>. <pub-id pub-id-type="doi">10.1002/2017JG004166</pub-id></citation></ref>
<ref id="B29"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Cray</surname> <given-names>H.</given-names></name> <name><surname>Pollard</surname> <given-names>W. H.</given-names></name></person-group> (<year>2015</year>). <article-title>Vegetation recovery patterns following permafrost disturbance in a low arctic vegetation recovery patterns following permafrost disturbance in a low arctic setting: case study of Herschel Island, Yukon, Canada.</article-title> <source><italic>Arct. Antarct. Alpine Res.</italic></source> <volume>47</volume> <fpage>99</fpage>&#x2013;<lpage>113</lpage>. <pub-id pub-id-type="doi">10.1657/AAAR0013-076</pub-id></citation></ref>
<ref id="B30"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Cunliffe</surname> <given-names>A. M.</given-names></name> <name><surname>Tanski</surname> <given-names>G.</given-names></name> <name><surname>Radosavljevic</surname> <given-names>B.</given-names></name> <name><surname>Palmer</surname> <given-names>W. F.</given-names></name> <name><surname>Sachs</surname> <given-names>T.</given-names></name> <name><surname>Lantuit</surname> <given-names>H.</given-names></name><etal/></person-group> (<year>2019</year>). <article-title>Rapid retreat of permafrost coastline observed with aerial drone photogrammetry.</article-title> <source><italic>Cryosphere</italic></source> <volume>13</volume> <fpage>1513</fpage>&#x2013;<lpage>1528</lpage>.</citation></ref>
<ref id="B31"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Dai</surname> <given-names>A.</given-names></name> <name><surname>Luo</surname> <given-names>D.</given-names></name> <name><surname>Song</surname> <given-names>M.</given-names></name> <name><surname>Liu</surname> <given-names>J.</given-names></name></person-group> (<year>2019</year>). <article-title>Arctic amplification is caused by sea-ice loss under increasing CO2.</article-title> <source><italic>Nat. Commun.</italic></source> <volume>10</volume>:<issue>121</issue>. <pub-id pub-id-type="doi">10.1038/s41467-018-07954-9</pub-id> <pub-id pub-id-type="pmid">30631051</pub-id></citation></ref>
<ref id="B32"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Dastillung</surname> <given-names>M.</given-names></name> <name><surname>Corbet</surname> <given-names>B.</given-names></name></person-group> (<year>1978</year>). &#x201C;<article-title>La geochimie organique des sediments marins profonds. I: hydrocarbures satures et insatures des sediments</article-title>,&#x201D; in <source><italic>Geochimie Organique Des Sediments Marins Profonds</italic></source>, <role>eds</role> <person-group person-group-type="editor"><name><surname>Cabanaz</surname> <given-names>A.</given-names></name> <name><surname>Pelet</surname> <given-names>R.</given-names></name></person-group> (<publisher-loc>Paris</publisher-loc>: <publisher-name>CNRS</publisher-name>), <fpage>293</fpage>&#x2013;<lpage>323</lpage>.</citation></ref>
<ref id="B33"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Debyser</surname> <given-names>Y.</given-names></name> <name><surname>Pelet</surname> <given-names>R.</given-names></name> <name><surname>Dastillung</surname> <given-names>M.</given-names></name></person-group> (<year>1977</year>). &#x201C;<article-title>Geochimie organique des sediments marins recents: Mer Noire, Baltique, Atlantique (Mauritanie)</article-title>,&#x201D; in <source><italic>Advanes in Organic Geohemistry</italic></source>, <role>eds</role> <person-group person-group-type="editor"><name><surname>Campos</surname> <given-names>R.</given-names></name> <name><surname>Goni</surname> <given-names>J.</given-names></name></person-group> (<publisher-loc>Madrid</publisher-loc>: Empresa Nacional Adaro de Investigaciones Mineras), <fpage>289</fpage>&#x2013;<lpage>320</lpage>.</citation></ref>
<ref id="B34"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Ding</surname> <given-names>B.</given-names></name> <name><surname>Rezanezhad</surname> <given-names>F.</given-names></name> <name><surname>Gharedaghloo</surname> <given-names>B.</given-names></name> <name><surname>Van Cappellen</surname> <given-names>P.</given-names></name> <name><surname>Passeport</surname> <given-names>E.</given-names></name></person-group> (<year>2019</year>). <article-title>Bioretention cells under cold climate conditions: Effects of freezing and thawing on water infiltration, soil structure, and nutrient removal.</article-title> <source><italic>Sci. Total Environ.</italic></source> <volume>649</volume> <fpage>749</fpage>&#x2013;<lpage>759</lpage>. <pub-id pub-id-type="doi">10.1016/j.scitotenv.2018.08.366</pub-id> <pub-id pub-id-type="pmid">30176485</pub-id></citation></ref>
<ref id="B35"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Dou</surname> <given-names>F.</given-names></name> <name><surname>Ping</surname> <given-names>C.-L.</given-names></name> <name><surname>Guo</surname> <given-names>L.</given-names></name> <name><surname>Jorgenson</surname> <given-names>T.</given-names></name></person-group> (<year>2008</year>). <article-title>Estimating the impact of seawater on the production of soil water-extractable organic carbon during coastal erosion.</article-title> <source><italic>J. Environ. Qual.</italic></source> <volume>37</volume> <fpage>2368</fpage>&#x2013;<lpage>2374</lpage>. <pub-id pub-id-type="doi">10.2134/jeq2007.0403</pub-id> <pub-id pub-id-type="pmid">18948491</pub-id></citation></ref>
<ref id="B36"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Drenzek</surname> <given-names>N. J.</given-names></name> <name><surname>Montlu&#x00E7;on</surname> <given-names>D. B.</given-names></name> <name><surname>Yunker</surname> <given-names>M. B.</given-names></name> <name><surname>Macdonald</surname> <given-names>R. W.</given-names></name> <name><surname>Eglinton</surname> <given-names>T. I.</given-names></name></person-group> (<year>2007</year>). <article-title>Constraints on the origin of sedimentary organic carbon in the Beaufort Sea from coupled molecular 13C and 14C measurements.</article-title> <source><italic>Mar. Chem.</italic></source> <volume>103</volume> <fpage>146</fpage>&#x2013;<lpage>162</lpage>. <pub-id pub-id-type="doi">10.1016/j.marchem.2006.06.017</pub-id></citation></ref>
<ref id="B37"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Dunton</surname> <given-names>K. H.</given-names></name> <name><surname>Weingartner</surname> <given-names>T.</given-names></name> <name><surname>Carmack</surname> <given-names>E. C.</given-names></name></person-group> (<year>2006</year>). <article-title>The nearshore western Beaufort Sea ecosystem: circulation and importance of terrestrial carbon in arctic coastal food webs.</article-title> <source><italic>Prog. Oceanogr.</italic></source> <volume>71</volume> <fpage>362</fpage>&#x2013;<lpage>378</lpage>. <pub-id pub-id-type="doi">10.1016/j.pocean.2006.09.011</pub-id></citation></ref>
<ref id="B38"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Dutta</surname> <given-names>K.</given-names></name> <name><surname>Schuur</surname> <given-names>E. A. G.</given-names></name> <name><surname>Neff</surname> <given-names>J. C.</given-names></name> <name><surname>Zimov</surname> <given-names>S. A.</given-names></name></person-group> (<year>2006</year>). <article-title>Potential carbon release from permafrost soils of Northeastern Siberia.</article-title> <source><italic>Glob. Change Biol.</italic></source> <volume>12</volume> <fpage>2336</fpage>&#x2013;<lpage>2351</lpage>. <pub-id pub-id-type="doi">10.1111/j.1365-2486.2006.01259.x</pub-id></citation></ref>
<ref id="B39"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Eglinton</surname> <given-names>G.</given-names></name> <name><surname>Hamilton</surname> <given-names>R. J.</given-names></name></person-group> (<year>1967</year>). <article-title>Leaf epicuticular waxes.</article-title> <source><italic>Science</italic></source> <volume>156</volume> <fpage>1322</fpage>&#x2013;<lpage>1334</lpage>. <pub-id pub-id-type="doi">10.2307/1721263</pub-id></citation></ref>
<ref id="B40"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Fierer</surname> <given-names>N.</given-names></name> <name><surname>Schimel</surname> <given-names>J. P.</given-names></name></person-group> (<year>2003</year>). <article-title>A proposed mechanism for the pulse in carbon dioxide production commonly observed following the rapid rewetting of a dry soil.</article-title> <source><italic>Soil Sci. Soc. Am. J.</italic></source> <volume>67</volume> <fpage>798</fpage>&#x2013;<lpage>805</lpage>. <pub-id pub-id-type="doi">10.2136/SSSAJ2003.7980</pub-id></citation></ref>
<ref id="B41"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Forbes</surname> <given-names>D.</given-names></name></person-group> (<year>2019</year>). &#x201C;<article-title>Chapter 8 - Arctic deltas and estuaries: a canadian perspective</article-title>,&#x201D; in <source><italic>Coasts and Estuaries The Future</italic></source>, <role>eds</role> <person-group person-group-type="editor"><name><surname>Wolanski</surname> <given-names>E.</given-names></name> <name><surname>Day</surname> <given-names>J. W.</given-names></name> <name><surname>Ellitt</surname> <given-names>M.</given-names></name> <name><surname>Ramachadran</surname> <given-names>R.</given-names></name></person-group> (<publisher-loc>Amsterdam</publisher-loc>: <publisher-name>Elsevier</publisher-name>).</citation></ref>
<ref id="B42"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Fritz</surname> <given-names>M.</given-names></name> <name><surname>Vonk</surname> <given-names>J. E.</given-names></name> <name><surname>Lantuit</surname> <given-names>H.</given-names></name></person-group> (<year>2017</year>). <article-title>Collapsing arctic coastlines.</article-title> <source><italic>Nat. Clim. Change</italic></source> <volume>7</volume> <fpage>6</fpage>&#x2013;<lpage>7</lpage>. <pub-id pub-id-type="doi">10.1038/nclimate3188</pub-id></citation></ref>
<ref id="B43"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Fritz</surname> <given-names>M.</given-names></name> <name><surname>Wetterich</surname> <given-names>S.</given-names></name> <name><surname>Schirrmeister</surname> <given-names>L.</given-names></name> <name><surname>Meyer</surname> <given-names>H.</given-names></name> <name><surname>Lantuit</surname> <given-names>H.</given-names></name> <name><surname>Preusser</surname> <given-names>F.</given-names></name><etal/></person-group> (<year>2012</year>). <article-title>Eastern Beringia and beyond: late Wisconsinan and Holocene landscape dynamics along the Yukon Coastal Plain, Canada.</article-title> <source><italic>Palaeogeogr. Palaeoclimatol. Palaeoecol.</italic></source> <volume>319&#x2013;320</volume> <fpage>28</fpage>&#x2013;<lpage>45</lpage>. <pub-id pub-id-type="doi">10.1016/j.palaeo.2011.12.015</pub-id></citation></ref>
<ref id="B44"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Glud</surname> <given-names>R.</given-names></name></person-group> (<year>2008</year>). <article-title>Oxygen dynamics of marine sediments.</article-title> <source><italic>Mar. Biol. Res.</italic></source> <volume>4</volume> <fpage>243</fpage>&#x2013;<lpage>289</lpage>. <pub-id pub-id-type="doi">10.1080/17451000801888726</pub-id></citation></ref>
<ref id="B45"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Go&#x00F1;i</surname> <given-names>M. A.</given-names></name> <name><surname>O&#x2019;Connor</surname> <given-names>A. E.</given-names></name> <name><surname>Kuzyk</surname> <given-names>Z. Z.</given-names></name> <name><surname>Yunker</surname> <given-names>M. B.</given-names></name> <name><surname>Gobeil</surname> <given-names>C.</given-names></name> <name><surname>Macdonald</surname> <given-names>R. W.</given-names></name></person-group> (<year>2013</year>). <article-title>Distribution and sources of organic matter in surface marine sediments across the North American Arctic margin.</article-title> <source><italic>J. Geophys. Res. Oceans</italic></source> <volume>118</volume> <fpage>4017</fpage>&#x2013;<lpage>4035</lpage>. <pub-id pub-id-type="doi">10.1002/jgrc.20286</pub-id></citation></ref>
<ref id="B46"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Go&#x00F1;i</surname> <given-names>M. A.</given-names></name> <name><surname>Yunker</surname> <given-names>M. B.</given-names></name> <name><surname>Macdonald</surname> <given-names>R. W.</given-names></name> <name><surname>Eglinton</surname> <given-names>T. I.</given-names></name></person-group> (<year>2005</year>). <article-title>The supply and preservation of ancient and modern components of organic carbon in the Canadian Beaufort Shelf of the Arctic Ocean.</article-title> <source><italic>Mar. Chem.</italic></source> <volume>93</volume> <fpage>53</fpage>&#x2013;<lpage>73</lpage>. <pub-id pub-id-type="doi">10.1016/j.marchem.2004.08.001</pub-id></citation></ref>
<ref id="B47"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Grimalt</surname> <given-names>J.</given-names></name> <name><surname>Albaig&#x00E9;s</surname> <given-names>J.</given-names></name></person-group> (<year>1987</year>). <article-title>Sources and occurrence of C12C22 n-alkane distributions with even carbon-number preference in sedimentary environments.</article-title> <source><italic>Geochim. Cosmochim. Acta</italic></source> <volume>51</volume> <fpage>1379</fpage>&#x2013;<lpage>1384</lpage>. <pub-id pub-id-type="doi">10.1016/0016-7037(87)90322-X</pub-id></citation></ref>
<ref id="B48"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Grotheer</surname> <given-names>H.</given-names></name> <name><surname>Meyer</surname> <given-names>V.</given-names></name> <name><surname>Riedel</surname> <given-names>T.</given-names></name> <name><surname>Pfalz</surname> <given-names>G.</given-names></name> <name><surname>Mathieu</surname> <given-names>L.</given-names></name> <name><surname>Hefter</surname> <given-names>J.</given-names></name><etal/></person-group> (<year>2020</year>). <article-title>Burial and origin of permafrost-derived carbon in the nearshore zone of the Southern Canadian Beaufort Sea.</article-title> <source><italic>Geophys. Res. Lett.</italic></source> <volume>47</volume>:<issue>e2019GL085897</issue>. <pub-id pub-id-type="doi">10.1029/2019GL085897</pub-id></citation></ref>
<ref id="B49"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Gundelwein</surname> <given-names>A.</given-names></name> <name><surname>M&#x00FC;ller-Lupp</surname> <given-names>T.</given-names></name> <name><surname>Sommerkorn</surname> <given-names>M.</given-names></name> <name><surname>Haupt</surname> <given-names>E. T. K.</given-names></name> <name><surname>Pfeiffer</surname> <given-names>E. M.</given-names></name> <name><surname>Wiechmann</surname> <given-names>H.</given-names></name></person-group> (<year>2007</year>). <article-title>Carbon in tundra soils in the Lake Labaz region of arctic Siberia.</article-title> <source><italic>Eur. J. Soil Sci.</italic></source> <volume>58</volume> <fpage>1164</fpage>&#x2013;<lpage>1174</lpage>. <pub-id pub-id-type="doi">10.1111/j.1365-2389.2007.00908.x</pub-id></citation></ref>
<ref id="B50"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>G&#x00FC;nther</surname> <given-names>F.</given-names></name> <name><surname>Overduin</surname> <given-names>P. P.</given-names></name> <name><surname>Sandakov</surname> <given-names>A. V.</given-names></name> <name><surname>Grosse</surname> <given-names>G.</given-names></name> <name><surname>Grigoriev</surname> <given-names>M. N.</given-names></name></person-group> (<year>2013</year>). <article-title>Short- and long-term thermo-erosion of ice-rich permafrost coasts in the Laptev Sea region.</article-title> <source><italic>Biogeosciences</italic></source> <volume>10</volume> <fpage>4297</fpage>&#x2013;<lpage>4318</lpage>. <pub-id pub-id-type="doi">10.5194/bg-10-4297-2013</pub-id></citation></ref>
<ref id="B51"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>G&#x00FC;nther</surname> <given-names>F.</given-names></name> <name><surname>Overduin</surname> <given-names>P. P.</given-names></name> <name><surname>Yakshina</surname> <given-names>I. A.</given-names></name> <name><surname>Opel</surname> <given-names>T.</given-names></name> <name><surname>Baranskaya</surname> <given-names>A. V.</given-names></name> <name><surname>Grigoriev</surname> <given-names>M. N.</given-names></name></person-group> (<year>2015</year>). <article-title>Observing Muostakh disappear: permafrost thaw subsidence and erosion of a ground-ice-rich Island in response to arctic summer warming and sea ice reduction.</article-title> <source><italic>Cryosphere</italic></source> <volume>9</volume> <fpage>151</fpage>&#x2013;<lpage>178</lpage>. <pub-id pub-id-type="doi">10.5194/tc-9-151-2015</pub-id></citation></ref>
<ref id="B52"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Harper</surname> <given-names>J. R.</given-names></name> <name><surname>Penland</surname> <given-names>P. S.</given-names></name></person-group> (<year>1982</year>). <source><italic>Beaufort Sea Sediment Dynamics. Contract Report to Atlantic Geoscience Centre.</italic></source> <publisher-loc>Ottawa, ON</publisher-loc>: <publisher-name>Geological Survey of Canada</publisher-name>.</citation></ref>
<ref id="B53"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Hequette</surname> <given-names>A.</given-names></name> <name><surname>Barnes</surname> <given-names>P. W.</given-names></name></person-group> (<year>1990</year>). <article-title>Coastal retreat and shoreface profile variations in the Canadian Beaufort Sea.</article-title> <source><italic>Mar. Geol.</italic></source> <volume>91</volume> <fpage>113</fpage>&#x2013;<lpage>132</lpage>. <pub-id pub-id-type="doi">10.1016/0025-3227(90)90136-8</pub-id></citation></ref>
<ref id="B54"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>H&#x00E9;quette</surname> <given-names>A.</given-names></name> <name><surname>Desrosiers</surname> <given-names>M.</given-names></name> <name><surname>Barnes</surname> <given-names>P. W.</given-names></name></person-group> (<year>1995</year>). <article-title>Sea ice scouring on the inner shelf of the southeastern Canadian Beaufort Sea.</article-title> <source><italic>Mar. Geol.</italic></source> <volume>128</volume> <fpage>201</fpage>&#x2013;<lpage>219</lpage>. <pub-id pub-id-type="doi">10.1016/0025-3227(95)00095-G</pub-id></citation></ref>
<ref id="B55"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Heslop</surname> <given-names>J. K.</given-names></name> <name><surname>Chandra</surname> <given-names>S.</given-names></name> <name><surname>Sobzcak</surname> <given-names>W. V.</given-names></name> <name><surname>Davydov</surname> <given-names>S. P.</given-names></name> <name><surname>Davydova</surname> <given-names>A. I.</given-names></name> <name><surname>Spektor</surname> <given-names>V. V.</given-names></name><etal/></person-group> (<year>2017</year>). <article-title>Variable respiration rates of incubated permafrost soil extracts from the Kolyma River lowlands, north-east Siberia.</article-title> <source><italic>Polar Res.</italic></source> <volume>37</volume>:<issue>1305157</issue>. <pub-id pub-id-type="doi">10.1080/17518369.2017.1305157</pub-id></citation></ref>
<ref id="B56"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Heyer</surname> <given-names>J.</given-names></name> <name><surname>H&#x00FC;bner</surname> <given-names>H.</given-names></name> <name><surname>Maa&#x03B2;</surname> <given-names>I.</given-names></name></person-group> (<year>1976</year>). <article-title>Isotopenfraktionierung des Kohlenstoffs bei der mikrobiellen Methanbildung.</article-title> <source><italic>Isotopenpraxis Isotop. Environ. Health Stud.</italic></source> <volume>12</volume> <fpage>202</fpage>&#x2013;<lpage>205</lpage>. <pub-id pub-id-type="doi">10.1080/10256017608543912</pub-id></citation></ref>
<ref id="B57"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Hilton</surname> <given-names>R. G.</given-names></name> <name><surname>Galy</surname> <given-names>V.</given-names></name> <name><surname>Gaillardet</surname> <given-names>J.</given-names></name> <name><surname>Dellinger</surname> <given-names>M.</given-names></name> <name><surname>Bryant</surname> <given-names>C.</given-names></name><etal/></person-group> (<year>2015</year>). <article-title>Erosion of organic carbon in the Arctic as a geological carbon dioxide sink.</article-title> <source><italic>Nature</italic></source> <volume>524</volume> <fpage>84</fpage>&#x2013;<lpage>87</lpage>. <pub-id pub-id-type="doi">10.1038/nature14653</pub-id> <pub-id pub-id-type="pmid">26245581</pub-id></citation></ref>
<ref id="B58"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>H&#x00F6;fle</surname> <given-names>S.</given-names></name> <name><surname>Rethemeyer</surname> <given-names>J.</given-names></name> <name><surname>Mueller</surname> <given-names>C. W.</given-names></name> <name><surname>John</surname> <given-names>S.</given-names></name></person-group> (<year>2013</year>). <article-title>Organic matter composition and stabilization in a polygonal tundra soil of the Lena Delta.</article-title> <source><italic>Biogeosciences</italic></source> <volume>10</volume> <fpage>3145</fpage>&#x2013;<lpage>3158</lpage>. <pub-id pub-id-type="doi">10.5194/bg-10-3145-2013</pub-id></citation></ref>
<ref id="B59"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Hugelius</surname> <given-names>G.</given-names></name> <name><surname>Strauss</surname> <given-names>J.</given-names></name> <name><surname>Zubrzycki</surname> <given-names>S.</given-names></name> <name><surname>Harden</surname> <given-names>J. W.</given-names></name> <name><surname>Schuur</surname> <given-names>E. A. G.</given-names></name> <name><surname>Ping</surname> <given-names>C. L.</given-names></name><etal/></person-group> (<year>2014</year>). <article-title>Estimated stocks of circumpolar permafrost carbon with quantified uncertainty ranges and identified data gaps.</article-title> <source><italic>Biogeosciences</italic></source> <volume>11</volume> <fpage>6573</fpage>&#x2013;<lpage>6593</lpage>. <pub-id pub-id-type="doi">10.5194/bg-11-6573-2014</pub-id></citation></ref>
<ref id="B60"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Huggett</surname> <given-names>W. S.</given-names></name> <name><surname>Woodward</surname> <given-names>M. J.</given-names></name> <name><surname>Stephenson</surname> <given-names>F.</given-names></name> <name><surname>Hermiston</surname> <given-names>F. V.</given-names></name> <name><surname>Douglas</surname> <given-names>A.</given-names></name></person-group> (<year>1975</year>). <source><italic>Near and Bottom Currents and Offshore Tides, Ocean and Aquatic Sciences, Beaufort Sea Technical Report No. 16.</italic></source> <publisher-loc>Victoria, BC</publisher-loc>: <publisher-name>Ocean and Aquatic Sciences Department of the Environment</publisher-name>.</citation></ref>
<ref id="B61"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Irrgang</surname> <given-names>A. M.</given-names></name> <name><surname>Lantuit</surname> <given-names>H.</given-names></name> <name><surname>Manson</surname> <given-names>G. K.</given-names></name> <name><surname>G&#x00FC;nther</surname> <given-names>F.</given-names></name> <name><surname>Grosse</surname> <given-names>G.</given-names></name> <name><surname>Overduin</surname> <given-names>P. P.</given-names></name></person-group> (<year>2018</year>). <article-title>Variability in rates of coastal change along the Yukon Coast, 1951 to 2015.</article-title> <source><italic>J. Geophys. Res. Earth Surf.</italic></source> <volume>123</volume> <fpage>779</fpage>&#x2013;<lpage>800</lpage>. <pub-id pub-id-type="doi">10.1002/2017JF004326</pub-id></citation></ref>
<ref id="B62"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>James</surname> <given-names>T. S.</given-names></name> <name><surname>Henton</surname> <given-names>J. A.</given-names></name> <name><surname>Leonard</surname> <given-names>L. J.</given-names></name> <name><surname>Darlington</surname> <given-names>A.</given-names></name> <name><surname>Forbes</surname> <given-names>D. L.</given-names></name> <name><surname>Craymer</surname> <given-names>M.</given-names></name></person-group> (<year>2014</year>). <article-title>Relative sea-level projections in Canada and the adjacent mainland United States.</article-title> <source><italic>Geol. Surv. Canada Open File</italic></source> <volume>7737</volume>:<issue>10.4095</issue>. <pub-id pub-id-type="doi">10.4095/295574</pub-id> <pub-id pub-id-type="pmid">295574</pub-id></citation></ref>
<ref id="B63"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Jones</surname> <given-names>B. M.</given-names></name> <name><surname>Arp</surname> <given-names>C. D.</given-names></name> <name><surname>Jorgenson</surname> <given-names>M. T.</given-names></name> <name><surname>Hinkel</surname> <given-names>K. M.</given-names></name> <name><surname>Schmutz</surname> <given-names>J. A.</given-names></name> <name><surname>Flint</surname> <given-names>P. L.</given-names></name></person-group> (<year>2009</year>). <article-title>Increase in the rate and uniformity of coastline erosion in Arctic Alaska.</article-title> <source><italic>Geophys. Res. Lett.</italic></source> <volume>36</volume> <fpage>1</fpage>&#x2013;<lpage>5</lpage>. <pub-id pub-id-type="doi">10.1029/2008GL036205</pub-id></citation></ref>
<ref id="B64"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Jones</surname> <given-names>B. M.</given-names></name> <name><surname>Farquharson</surname> <given-names>L. M.</given-names></name> <name><surname>Baughman</surname> <given-names>C. A.</given-names></name> <name><surname>Buzard</surname> <given-names>R. M.</given-names></name> <name><surname>Arp</surname> <given-names>C. D.</given-names></name> <name><surname>Grosse</surname> <given-names>G.</given-names></name><etal/></person-group> (<year>2018</year>). <article-title>A decade of remotely sensed observations highlight complex processes linked to coastal permafrost bluff erosion in the Arctic A decade of remotely sensed observations highlight complex processes linked to coastal permafrost bluff eros.</article-title> <source><italic>Environ. Res. Lett.</italic></source> <volume>13</volume>:<issue>115001</issue>. <pub-id pub-id-type="doi">10.1088/1748-9326/aae471</pub-id></citation></ref>
<ref id="B65"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Jong</surname> <given-names>D.</given-names></name> <name><surname>Br&#x00F6;der</surname> <given-names>L.</given-names></name> <name><surname>Tanski</surname> <given-names>G.</given-names></name> <name><surname>Fritz</surname> <given-names>M.</given-names></name> <name><surname>Lantuit</surname> <given-names>H.</given-names></name> <name><surname>Tesi</surname> <given-names>T.</given-names></name><etal/></person-group> (<year>2020</year>). <article-title>Nearshore zone dynamics determine pathway of organic carbon from eroding permafrost coasts.</article-title> <source><italic>Geophys. Res. Lett.</italic></source> <volume>47</volume>:<issue>e2020GL088561</issue>. <pub-id pub-id-type="doi">10.1029/2020GL088561</pub-id> <pub-id pub-id-type="pmid">32999517</pub-id></citation></ref>
<ref id="B66"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Karlsson</surname> <given-names>E. S.</given-names></name> <name><surname>Br&#x00FC;chert</surname> <given-names>V.</given-names></name> <name><surname>Tesi</surname> <given-names>T.</given-names></name> <name><surname>Charkin</surname> <given-names>A.</given-names></name> <name><surname>Dudarev</surname> <given-names>O.</given-names></name> <name><surname>Semiletov</surname> <given-names>I.</given-names></name><etal/></person-group> (<year>2015</year>). <article-title>Contrasting regimes for organic matter degradation in the East Siberian Sea and the Laptev Sea assessed through microbial incubations and molecular markers.</article-title> <source><italic>Mar. Chem.</italic></source> <volume>170</volume> <fpage>11</fpage>&#x2013;<lpage>22</lpage>. <pub-id pub-id-type="doi">10.1016/J.MARCHEM.2014.12.005</pub-id></citation></ref>
<ref id="B67"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Kaufman</surname> <given-names>D. S.</given-names></name> <name><surname>Schneider</surname> <given-names>D. P.</given-names></name> <name><surname>McKay</surname> <given-names>N. P.</given-names></name> <name><surname>Ammann</surname> <given-names>C. M.</given-names></name> <name><surname>Bradley</surname> <given-names>R. S.</given-names></name> <name><surname>Briffa</surname> <given-names>K. R.</given-names></name><etal/></person-group> (<year>2009</year>). <article-title>Recent warming reverses long-term arctic cooling.</article-title> <source><italic>Science</italic></source> <volume>325</volume> <fpage>1236</fpage>&#x2013;<lpage>1239</lpage>. <pub-id pub-id-type="doi">10.1126/science.1173983</pub-id> <pub-id pub-id-type="pmid">19729653</pub-id></citation></ref>
<ref id="B68"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Kennedy</surname> <given-names>C. E.</given-names></name> <name><surname>Smith</surname> <given-names>C. A. S.</given-names></name> <name><surname>Cooley</surname> <given-names>D. A.</given-names></name></person-group> (<year>2001</year>). <article-title>Observations of change in the cover of polargrass, Arctagrostis latifolia, and arctic lupine, Lupinus arcticus, in upland tundra on Herschel Island, Yukon Territory.</article-title> <source><italic>Can. Field Natural.</italic></source> <volume>115</volume> <fpage>323</fpage>&#x2013;<lpage>328</lpage>.</citation></ref>
<ref id="B69"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Killops</surname> <given-names>S.</given-names></name> <name><surname>Killops</surname> <given-names>V.</given-names></name></person-group> (<year>2004</year>). <source><italic>Introduction to Organic Geochemistry.</italic></source> <publisher-loc>Harlow</publisher-loc>: <publisher-name>Longman Scientific &#x0026; Technical</publisher-name>.</citation></ref>
<ref id="B70"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Klein</surname> <given-names>K. P.</given-names></name> <name><surname>Lantuit</surname> <given-names>H.</given-names></name> <name><surname>Heim</surname> <given-names>B.</given-names></name> <name><surname>Fell</surname> <given-names>F.</given-names></name> <name><surname>Doxaran</surname> <given-names>D.</given-names></name> <name><surname>Irrgang</surname> <given-names>A. M.</given-names></name></person-group> (<year>2019</year>). <article-title>Long-term high-resolution sediment and sea surface temperature spatial patterns in arctic nearshore waters retrieved using 30-year landsat archive imagery.</article-title> <source><italic>Remote Sens.</italic></source> <volume>11</volume>:<issue>2791</issue>. <pub-id pub-id-type="doi">10.3390/rs11232791</pub-id></citation></ref>
<ref id="B71"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Knoblauch</surname> <given-names>C.</given-names></name> <name><surname>Beer</surname> <given-names>C.</given-names></name> <name><surname>Liebner</surname> <given-names>S.</given-names></name> <name><surname>Grigoriev</surname> <given-names>M. N.</given-names></name> <name><surname>Pfeiffer</surname> <given-names>E. M.</given-names></name></person-group> (<year>2018</year>). <article-title>Methane production as key to the greenhouse gas budget of thawing permafrost.</article-title> <source><italic>Nat. Clim. Change</italic></source> <volume>8</volume> <fpage>1</fpage>&#x2013;<lpage>4</lpage>. <pub-id pub-id-type="doi">10.1038/s41558-018-0095-z</pub-id></citation></ref>
<ref id="B72"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Knoblauch</surname> <given-names>C.</given-names></name> <name><surname>Beer</surname> <given-names>C.</given-names></name> <name><surname>Sosnin</surname> <given-names>A.</given-names></name> <name><surname>Wagner</surname> <given-names>D.</given-names></name> <name><surname>Pfeiffer</surname> <given-names>E. M.</given-names></name></person-group> (<year>2013</year>). <article-title>Predicting long-term carbon mineralization and trace gas production from thawing permafrost of Northeast Siberia.</article-title> <source><italic>Glob. Change Biol.</italic></source> <volume>19</volume> <fpage>1160</fpage>&#x2013;<lpage>1172</lpage>. <pub-id pub-id-type="doi">10.1111/gcb.12116</pub-id> <pub-id pub-id-type="pmid">23504893</pub-id></citation></ref>
<ref id="B73"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Kokelj</surname> <given-names>S. V.</given-names></name> <name><surname>Lacelle</surname> <given-names>D.</given-names></name> <name><surname>Lantz</surname> <given-names>T. C.</given-names></name> <name><surname>Tunnicliffe</surname> <given-names>J.</given-names></name> <name><surname>Malone</surname> <given-names>L.</given-names></name> <name><surname>Clark</surname> <given-names>I. D.</given-names></name><etal/></person-group> (<year>2013</year>). <article-title>Thawing of massive ground ice in mega slumps drives increases in stream sediment and solute flux across a range of watershed scales.</article-title> <source><italic>J. Geophys. Res. Earth Surf.</italic></source> <volume>118</volume> <fpage>681</fpage>&#x2013;<lpage>692</lpage>. <pub-id pub-id-type="doi">10.1002/jgrf.20063</pub-id></citation></ref>
<ref id="B74"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Kokelj</surname> <given-names>S. V.</given-names></name> <name><surname>Smith</surname> <given-names>C. A. S.</given-names></name> <name><surname>Burn</surname> <given-names>C. R.</given-names></name></person-group> (<year>2002</year>). <article-title>Physical and chemical characteristics of the active layer and permafrost, Herschel Island, western Arctic Coast, Canada.</article-title> <source><italic>Permafrost Periglac. Process.</italic></source> <volume>13</volume> <fpage>171</fpage>&#x2013;<lpage>185</lpage>. <pub-id pub-id-type="doi">10.1002/ppp.417</pub-id></citation></ref>
<ref id="B75"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Kristensen</surname> <given-names>E.</given-names></name> <name><surname>Ahmed</surname> <given-names>S. I.</given-names></name> <name><surname>Devol</surname> <given-names>A. H.</given-names></name></person-group> (<year>1995</year>). <article-title>Aerobic and anaerobic decomposition of organic matter in marine sediment: which is fastest?</article-title> <source><italic>Limnol. Oceanogr.</italic></source> <volume>40</volume> <fpage>1430</fpage>&#x2013;<lpage>1437</lpage>. <pub-id pub-id-type="doi">10.4319/lo.1995.40.8.1430</pub-id></citation></ref>
<ref id="B76"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Kuhry</surname> <given-names>P.</given-names></name> <name><surname>Vitt</surname> <given-names>D. H.</given-names></name></person-group> (<year>1996</year>). <article-title>Fossil carbon/nitrogen ratios as a measure of peat decomposition.</article-title> <source><italic>Ecol. Soc. Am.</italic></source> <volume>77</volume> <fpage>271</fpage>&#x2013;<lpage>275</lpage>. <pub-id pub-id-type="doi">10.2307/2265676</pub-id></citation></ref>
<ref id="B77"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Kvenvolden</surname> <given-names>K.</given-names></name></person-group> (<year>1970</year>). &#x201C;<article-title>Evidence for transformation of normal fatty acids in sediments</article-title>,&#x201D; in <source><italic>Advances in Organic Geochemistry</italic></source> <volume>1966</volume> <role>eds</role> <person-group person-group-type="editor"><name><surname>Hobson</surname> <given-names>G. D.</given-names></name> <name><surname>Speers</surname> <given-names>G. C.</given-names></name></person-group> (<publisher-loc>Oxford</publisher-loc>: <publisher-name>Pergamon Press</publisher-name>), <fpage>335</fpage>&#x2013;<lpage>366</lpage>.</citation></ref>
<ref id="B78"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Lamb</surname> <given-names>A. L.</given-names></name> <name><surname>Wilson</surname> <given-names>G. P.</given-names></name> <name><surname>Leng</surname> <given-names>M. J.</given-names></name></person-group> (<year>2006</year>). <article-title>A review of coastal palaeoclimate and relative sea-level reconstructions using &#x03B4;13C and C/N ratios in organic material.</article-title> <source><italic>Earth Sci. Rev.</italic></source> <volume>75</volume> <fpage>29</fpage>&#x2013;<lpage>57</lpage>. <pub-id pub-id-type="doi">10.1016/j.earscirev.2005.10.003</pub-id></citation></ref>
<ref id="B79"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Lantuit</surname> <given-names>H.</given-names></name> <name><surname>Overduin</surname> <given-names>P. P.</given-names></name> <name><surname>Couture</surname> <given-names>N.</given-names></name> <name><surname>Wetterich</surname> <given-names>S.</given-names></name> <name><surname>Ar&#x00E9;</surname> <given-names>F.</given-names></name> <name><surname>Atkinson</surname> <given-names>D.</given-names></name><etal/></person-group> (<year>2012</year>). <article-title>The arctic coastal dynamics database: a new classification scheme and statistics on arctic permafrost coastlines.</article-title> <source><italic>Estuar. Coasts</italic></source> <volume>35</volume> <fpage>383</fpage>&#x2013;<lpage>400</lpage>. <pub-id pub-id-type="doi">10.1007/s12237-010-9362-6</pub-id></citation></ref>
<ref id="B80"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Lantuit</surname> <given-names>H.</given-names></name> <name><surname>Pollard</surname> <given-names>W. H.</given-names></name></person-group> (<year>2005</year>). <article-title>Temporal stereophotogrammetric analysis of retrogressive thaw slumps on Herschel Island, Yukon Territory.</article-title> <source><italic>Nat. Haz. Earth Syst. Sci.</italic></source> <volume>5</volume> <fpage>413</fpage>&#x2013;<lpage>423</lpage>. <pub-id pub-id-type="doi">10.5194/nhess-5-413-2005</pub-id></citation></ref>
<ref id="B81"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Lantuit</surname> <given-names>H.</given-names></name> <name><surname>Pollard</surname> <given-names>W. H.</given-names></name></person-group> (<year>2008</year>). <article-title>Fifty years of coastal erosion and retrogressive thaw slump activity on Herschel Island, southern Beaufort Sea, Yukon Territory, Canada.</article-title> <source><italic>Geomorphology</italic></source> <volume>95</volume> <fpage>84</fpage>&#x2013;<lpage>102</lpage>. <pub-id pub-id-type="doi">10.1016/j.geomorph.2006.07.040</pub-id></citation></ref>
<ref id="B82"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Lee</surname> <given-names>H.</given-names></name> <name><surname>Schuur</surname> <given-names>E. A. G.</given-names></name> <name><surname>Inglett</surname> <given-names>K. S.</given-names></name> <name><surname>Lavoie</surname> <given-names>M.</given-names></name> <name><surname>Chanton</surname> <given-names>J. P.</given-names></name></person-group> (<year>2012</year>). <article-title>The rate of permafrost carbon release under aerobic and anaerobic conditions and its potential effects on climate.</article-title> <source><italic>Glob. Change Biol.</italic></source> <volume>18</volume> <fpage>515</fpage>&#x2013;<lpage>527</lpage>. <pub-id pub-id-type="doi">10.1111/j.1365-2486.2011.02519.x</pub-id></citation></ref>
<ref id="B83"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Li</surname> <given-names>G.</given-names></name> <name><surname>Li</surname> <given-names>L.</given-names></name> <name><surname>Tarozo</surname> <given-names>R.</given-names></name> <name><surname>Longo</surname> <given-names>W. M.</given-names></name> <name><surname>Wang</surname> <given-names>K. J.</given-names></name> <name><surname>Dong</surname> <given-names>H.</given-names></name><etal/></person-group> (<year>2018</year>). <article-title>Microbial production of long-chain n-alkanes: implication for interpreting sedimentary leaf wax signals.</article-title> <source><italic>Organ. Geochem.</italic></source> <volume>115</volume> <fpage>24</fpage>&#x2013;<lpage>31</lpage>. <pub-id pub-id-type="doi">10.1016/j.orggeochem.2017.10.005</pub-id></citation></ref>
<ref id="B84"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Littlefair</surname> <given-names>C. A.</given-names></name> <name><surname>Tank</surname> <given-names>S. E.</given-names></name> <name><surname>Kokelj</surname> <given-names>S. V.</given-names></name></person-group> (<year>2017</year>). <article-title>Retrogressive thaw slumps temper dissolved organic carbon delivery to streams of the Peel Plateau, NWT, Canada.</article-title> <source><italic>Biogeosciences</italic></source> <volume>14</volume> <fpage>5487</fpage>&#x2013;<lpage>5505</lpage>. <pub-id pub-id-type="doi">10.5194/bg-14-5487-2017</pub-id></citation></ref>
<ref id="B85"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Macdonald</surname> <given-names>R. W.</given-names></name> <name><surname>Kuzyk</surname> <given-names>Z. Z. A.</given-names></name> <name><surname>Johanessen</surname> <given-names>S. C.</given-names></name></person-group> (<year>2015</year>). <article-title>The vulnerability of Arctic shelf sediments to climate change.</article-title> <source><italic>Environ. Rev.</italic></source> <volume>23</volume> <fpage>461</fpage>&#x2013;<lpage>479</lpage>. <pub-id pub-id-type="doi">10.1139/er-2015-0040</pub-id></citation></ref>
<ref id="B86"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Mack</surname> <given-names>M. C.</given-names></name> <name><surname>Schuur</surname> <given-names>E. A. G.</given-names></name> <name><surname>Bret-Harte</surname> <given-names>M. S.</given-names></name> <name><surname>Shaver</surname> <given-names>G. R.</given-names></name> <name><surname>Chapin</surname> <given-names>F. S.</given-names></name></person-group> (<year>2004</year>). <article-title>Ecosystem carbon storage in arctic tundra reduce by long-term nutrient fertilization.</article-title> <source><italic>Nature</italic></source> <volume>431</volume> <fpage>440</fpage>&#x2013;<lpage>443</lpage>. <pub-id pub-id-type="doi">10.1038/nature02887</pub-id> <pub-id pub-id-type="pmid">15386009</pub-id></citation></ref>
<ref id="B87"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Mann</surname> <given-names>P. J.</given-names></name> <name><surname>Eglinton</surname> <given-names>T. I.</given-names></name> <name><surname>McIntyre</surname> <given-names>C. P.</given-names></name> <name><surname>Zimov</surname> <given-names>N.</given-names></name> <name><surname>Davydova</surname> <given-names>A.</given-names></name> <name><surname>Vonk</surname> <given-names>J. E.</given-names></name><etal/></person-group> (<year>2015</year>). <article-title>Utilization of ancient permafrost carbon in headwaters of Arctic fluvial networks.</article-title> <source><italic>Nat. Commun.</italic></source> <volume>6</volume>:<issue>7856</issue>. <pub-id pub-id-type="doi">10.1038/ncomms8856</pub-id> <pub-id pub-id-type="pmid">26206473</pub-id></citation></ref>
<ref id="B88"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Manson</surname> <given-names>G. K.</given-names></name> <name><surname>Solomon</surname> <given-names>S. M.</given-names></name></person-group> (<year>2007</year>). <article-title>Past and future forcing of Beaufort Sea coastal change.</article-title> <source><italic>Atmosphere Ocean</italic></source> <volume>45</volume> <fpage>107</fpage>&#x2013;<lpage>122</lpage>. <pub-id pub-id-type="doi">10.3137/ao.450204</pub-id></citation></ref>
<ref id="B89"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Manson</surname> <given-names>G. K.</given-names></name> <name><surname>Solomon</surname> <given-names>S. M.</given-names></name> <name><surname>Forbes</surname> <given-names>D. L.</given-names></name> <name><surname>Atkinson</surname> <given-names>D. E.</given-names></name> <name><surname>Craymer</surname> <given-names>M.</given-names></name></person-group> (<year>2005</year>). <article-title>Spatial variability of factors influencing coastal change in the Western Canadian Arctic.</article-title> <source><italic>Geo Mar. Lett.</italic></source> <volume>25</volume> <fpage>138</fpage>&#x2013;<lpage>145</lpage>. <pub-id pub-id-type="doi">10.1007/s00367-004-0195-9</pub-id></citation></ref>
<ref id="B90"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Mathis</surname> <given-names>J. T.</given-names></name> <name><surname>Pickart</surname> <given-names>R. S.</given-names></name> <name><surname>Byrne</surname> <given-names>R. H.</given-names></name> <name><surname>McNeil</surname> <given-names>C. L.</given-names></name> <name><surname>Moore</surname> <given-names>G. W. K.</given-names></name> <name><surname>Juranek</surname> <given-names>L. W.</given-names></name><etal/></person-group> (<year>2012</year>). <article-title>Storm-induced upwelling of high <italic>p</italic> CO<sub>2</sub> waters onto the continental shelf of the western Arctic Ocean and implications for carbonate mineral saturation states.</article-title> <source><italic>Geophysical Research Letters</italic></source> <volume>39</volume> <pub-id pub-id-type="doi">10.1029/2012GL051574</pub-id></citation></ref>
<ref id="B91"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>McGuire</surname> <given-names>A.</given-names></name> <name><surname>Anderson</surname> <given-names>L.</given-names></name> <name><surname>Christensen</surname> <given-names>T. R.</given-names></name> <name><surname>Dallimore</surname> <given-names>S.</given-names></name> <name><surname>Guo</surname> <given-names>L.</given-names></name> <name><surname>Hayes</surname> <given-names>D.</given-names></name><etal/></person-group> (<year>2009</year>). <article-title>Sensitivity of the carbon cycle in the Arctic to climate change.</article-title> <source><italic>Ecol. Monogr.</italic></source> <volume>79</volume> <fpage>523</fpage>&#x2013;<lpage>555</lpage>. <pub-id pub-id-type="doi">10.1890/08-2025.1</pub-id></citation></ref>
<ref id="B92"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>McGuire</surname> <given-names>A. D.</given-names></name> <name><surname>Lawrence</surname> <given-names>D. M.</given-names></name> <name><surname>Koven</surname> <given-names>C.</given-names></name> <name><surname>Clein</surname> <given-names>J. S.</given-names></name> <name><surname>Burke</surname> <given-names>E.</given-names></name> <name><surname>Chen</surname> <given-names>G.</given-names></name></person-group> (<year>2018</year>). <article-title>Dependence of the evolution of carbon dynamics in the northern permafrost region on the trajectory of climate change.</article-title> <source><italic>Proc. Natl. Acad. Sci. U.S.A.</italic></source> <volume>115</volume> <fpage>3882</fpage>&#x2013;<lpage>3887</lpage>. <pub-id pub-id-type="doi">10.1073/pnas.1719903115</pub-id> <pub-id pub-id-type="pmid">29581283</pub-id></citation></ref>
<ref id="B93"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Millero</surname> <given-names>F.</given-names></name> <name><surname>Huang</surname> <given-names>F.</given-names></name> <name><surname>Graham</surname> <given-names>T.</given-names></name> <name><surname>Pierrot</surname> <given-names>D.</given-names></name></person-group> (<year>2007</year>). <article-title>The dissociation of carbonic acid in NaCl solutions as a function of concentration and temperature.</article-title> <source><italic>Geochim. Cosmochim. Acta</italic></source> <volume>71</volume> <fpage>46</fpage>&#x2013;<lpage>55</lpage>. <pub-id pub-id-type="doi">10.1016/j.gca.2006.08.041</pub-id></citation></ref>
<ref id="B94"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Naidu</surname> <given-names>A. S.</given-names></name> <name><surname>Cooper</surname> <given-names>L. W.</given-names></name> <name><surname>Finney</surname> <given-names>B. P.</given-names></name> <name><surname>Macdonald</surname> <given-names>R. W.</given-names></name> <name><surname>Alexander</surname> <given-names>C.</given-names></name> <name><surname>Semiletov</surname> <given-names>I. P.</given-names></name></person-group> (<year>2000</year>). <article-title>Organic carbon isotope ratio (&#x03B4;<sup>13</sup>C) of Arctic Amerasian Continental shelf sediments.</article-title> <source><italic>Int. J. Earth Sci.</italic></source> <volume>89</volume> <fpage>522</fpage>&#x2013;<lpage>532</lpage>. <pub-id pub-id-type="doi">10.1007/s005310000121</pub-id></citation></ref>
<ref id="B95"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Neff</surname> <given-names>J. C.</given-names></name> <name><surname>Asner</surname> <given-names>G. P.</given-names></name></person-group> (<year>2001</year>). <article-title>Dissolved organic carbon in terrestrial ecosystems: synthesis and a model.</article-title> <source><italic>Ecosystems</italic></source> <volume>4</volume> <fpage>29</fpage>&#x2013;<lpage>48</lpage>. <pub-id pub-id-type="doi">10.1007/s100210000058</pub-id></citation></ref>
<ref id="B96"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Nielsen</surname> <given-names>D. M.</given-names></name> <name><surname>Dobrynin</surname> <given-names>M.</given-names></name> <name><surname>Baehr</surname> <given-names>J.</given-names></name> <name><surname>Razumov</surname> <given-names>S.</given-names></name> <name><surname>Grigoriev</surname> <given-names>M.</given-names></name></person-group> (<year>2020</year>). <article-title>Coastal erosion variability at the southern laptev sea linked to winter sea ice and the arctic oscillation.</article-title> <source><italic>Geophys. Res. Lett.</italic></source> <volume>47</volume>:<issue>e2019GL086876</issue>. <pub-id pub-id-type="doi">10.1029/2019GL086876</pub-id></citation></ref>
<ref id="B97"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Obu</surname> <given-names>J.</given-names></name> <name><surname>Lantuit</surname> <given-names>H.</given-names></name> <name><surname>Fritz</surname> <given-names>M.</given-names></name> <name><surname>Pollard</surname> <given-names>W. H.</given-names></name> <name><surname>Sachs</surname> <given-names>T.</given-names></name> <name><surname>G&#x00FC;nther</surname> <given-names>F.</given-names></name></person-group> (<year>2016</year>). <article-title>Relation between planimetric and volumetric measurements of permafrost coast erosion: a case study from Herschel Island, western Canadian Arctic.</article-title> <source><italic>Polar Res</italic>.</source> <volume>35</volume>:<issue>30313</issue>. <pub-id pub-id-type="doi">10.3402/polar.v35.30313</pub-id></citation></ref>
<ref id="B98"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Obu</surname> <given-names>J.</given-names></name> <name><surname>Lantuit</surname> <given-names>H.</given-names></name> <name><surname>Grosse</surname> <given-names>G.</given-names></name> <name><surname>G&#x00FC;nther</surname> <given-names>F.</given-names></name> <name><surname>Sachs</surname> <given-names>T.</given-names></name> <name><surname>Helm</surname> <given-names>V.</given-names></name><etal/></person-group> (<year>2015</year>). <article-title>Coastal erosion and mass wasting along the Canadian Beaufort Sea based on annual airborne LiDAR elevation data.</article-title> <source><italic>Geomorphology</italic></source> <volume>293</volume> <fpage>331</fpage>&#x2013;<lpage>346</lpage>. <pub-id pub-id-type="doi">10.1016/j.geomorph.2016.02.014</pub-id></citation></ref>
<ref id="B99"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Overduin</surname> <given-names>P. P.</given-names></name> <name><surname>Liebner</surname> <given-names>S.</given-names></name> <name><surname>Knoblauch</surname> <given-names>C.</given-names></name> <name><surname>G&#x00FC;nther</surname> <given-names>F.</given-names></name> <name><surname>Wetterich</surname> <given-names>S.</given-names></name> <name><surname>Schirrmeister</surname> <given-names>L.</given-names></name><etal/></person-group> (<year>2015</year>). <article-title>Methane oxidation following submarine permafrost degradation: measurements from a central Laptev Sea shelf borehole.</article-title> <source><italic>J. Geophys. Res. G Biogeosci.</italic></source> <volume>120</volume> <fpage>965</fpage>&#x2013;<lpage>978</lpage>. <pub-id pub-id-type="doi">10.1002/2014JG002862</pub-id></citation></ref>
<ref id="B100"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Overeem</surname> <given-names>I.</given-names></name> <name><surname>Anderson</surname> <given-names>R. S.</given-names></name> <name><surname>Wobus</surname> <given-names>C. W.</given-names></name> <name><surname>Clow</surname> <given-names>G. D.</given-names></name> <name><surname>Urban</surname> <given-names>F. E.</given-names></name> <name><surname>Matell</surname> <given-names>N.</given-names></name></person-group> (<year>2011</year>). <article-title>Sea ice loss enhances wave action at the Arctic coast.</article-title> <source><italic>Geophys. Res. Lett.</italic></source> <volume>38</volume> <fpage>1</fpage>&#x2013;<lpage>6</lpage>. <pub-id pub-id-type="doi">10.1029/2011GL048681</pub-id></citation></ref>
<ref id="B101"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Pelletier</surname> <given-names>B. R.</given-names></name> <name><surname>Medioli</surname> <given-names>B. E.</given-names></name></person-group> (<year>2014</year>). <article-title>Environmental atlas of the Beaufort coastlands.</article-title> <source><italic>Geol. Surv. Canada Open File</italic></source> <volume>7619</volume> <fpage>1</fpage>&#x2013;<lpage>271</lpage>. <pub-id pub-id-type="doi">10.4095/294601</pub-id></citation></ref>
<ref id="B102"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Pipko</surname> <given-names>I. I.</given-names></name> <name><surname>Pugach</surname> <given-names>S. P.</given-names></name> <name><surname>Semiletov</surname> <given-names>I. P.</given-names></name> <name><surname>Anderson</surname> <given-names>L. G.</given-names></name> <name><surname>Shakhova</surname> <given-names>N. E.</given-names></name> <name><surname>Gustafsson</surname> <given-names>&#x00D6;, et al.</given-names></name></person-group> (<year>2017</year>). <article-title>The spatial and interannual dynamics of the surface water carbonate system and air-sea CO2 fluxes in the outer shelf and slope of the Eurasian Arctic Ocean.</article-title> <source><italic>Ocean Sci.</italic></source> <volume>13</volume> <fpage>997</fpage>&#x2013;<lpage>1016</lpage>. <pub-id pub-id-type="doi">10.5194/os-13-997-2017</pub-id></citation></ref>
<ref id="B103"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Pollard</surname> <given-names>W.</given-names></name></person-group> (<year>1990</year>). &#x201C;<article-title>The nature and origin of ground ice in the Herschel Island area, Yukon Territory</article-title>,&#x201D; in <source><italic>Proceedings of the Fifth Canadian Conference on Permafrost</italic></source>, <publisher-loc>Perg&#x00E9;lisol</publisher-loc>, <fpage>23</fpage>&#x2013;<lpage>30</lpage>.</citation></ref>
<ref id="B104"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Radosavljevic</surname> <given-names>B.</given-names></name> <name><surname>Lantuit</surname> <given-names>H.</given-names></name> <name><surname>Pollard</surname> <given-names>W. H.</given-names></name> <name><surname>Overduin</surname> <given-names>P.</given-names></name> <name><surname>Couture</surname> <given-names>N.</given-names></name> <name><surname>Sachs</surname> <given-names>T.</given-names></name><etal/></person-group> (<year>2016</year>). <article-title>Erosion and flooding &#x2014; threats to coastal infrastructure in the arctic: a case study from Herschel Island, Yukon Territory, Canada.</article-title> <source><italic>Estuar. Coasts</italic></source> <volume>39</volume> <fpage>900</fpage>&#x2013;<lpage>915</lpage>. <pub-id pub-id-type="doi">10.1007/s12237-015-0046-0</pub-id></citation></ref>
<ref id="B105"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Ramage</surname> <given-names>J. L.</given-names></name> <name><surname>Fortier</surname> <given-names>D.</given-names></name> <name><surname>Hugelius</surname> <given-names>G.</given-names></name> <name><surname>Lantuit</surname> <given-names>H.</given-names></name> <name><surname>Morgenstern</surname> <given-names>A.</given-names></name></person-group> (<year>2019</year>). <article-title>Distribution of carbon and nitrogen along hillslopes in three valleys on Herschel Island, Yukon Territory, Canada.</article-title> <source><italic>Catena</italic></source> <volume>178</volume> <fpage>132</fpage>&#x2013;<lpage>140</lpage>. <pub-id pub-id-type="doi">10.1016/j.catena.2019.02.029</pub-id></citation></ref>
<ref id="B106"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Ramage</surname> <given-names>J. L.</given-names></name> <name><surname>Irrgang</surname> <given-names>A. M.</given-names></name> <name><surname>Herzschuh</surname> <given-names>U.</given-names></name> <name><surname>Morgenstern</surname> <given-names>A.</given-names></name> <name><surname>Couture</surname> <given-names>N.</given-names></name> <name><surname>Lantuit</surname> <given-names>H.</given-names></name></person-group> (<year>2017</year>). <article-title>Terrain controls on the occurrence of coastal retrogressive thaw slumps along the Yukon Coast, Canada.</article-title> <source><italic>J. Geophys. Res. Earth Surf.</italic></source> <volume>122</volume> <fpage>1619</fpage>&#x2013;<lpage>1634</lpage>. <pub-id pub-id-type="doi">10.1002/2017JF004231</pub-id></citation></ref>
<ref id="B107"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Rampton</surname> <given-names>V. N.</given-names></name></person-group> (<year>1982</year>). <article-title>Quaternary geology of the Yukon Coastal Plain.</article-title> <source><italic>Geol. Surv. Canada Bull.</italic></source> <volume>317</volume>:<issue>49</issue>.</citation></ref>
<ref id="B108"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Rasmussen</surname> <given-names>H.</given-names></name> <name><surname>Jorgensen</surname> <given-names>B. B.</given-names></name></person-group> (<year>1992</year>). <article-title>Microelectrode studies of seasonal oxygen uptake in a coastal sediment: role of molecular diffusion.</article-title> <source><italic>Mar. Ecol. Prog. Ser.</italic></source> <volume>81</volume> <fpage>289</fpage>&#x2013;<lpage>303</lpage>. <pub-id pub-id-type="doi">10.3354/meps081289</pub-id></citation></ref>
<ref id="B109"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Rielley</surname> <given-names>G.</given-names></name> <name><surname>Collier</surname> <given-names>R. J.</given-names></name> <name><surname>Jones</surname> <given-names>D. M.</given-names></name> <name><surname>Eglinton</surname> <given-names>G.</given-names></name></person-group> (<year>1991</year>). <article-title>The biogeochemistry of Ellesmere Lake, U.K.-I: source correlation of leaf wax inputs to the sedimentary lipid record.</article-title> <source><italic>Organ. Geochem.</italic></source> <volume>17</volume> <fpage>901</fpage>&#x2013;<lpage>912</lpage>. <pub-id pub-id-type="doi">10.1016/0146-6380(91)90031-E</pub-id></citation></ref>
<ref id="B110"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Ruff</surname> <given-names>M.</given-names></name> <name><surname>Fahrni</surname> <given-names>S.</given-names></name> <name><surname>G&#x00E4;ggeler</surname> <given-names>H. W.</given-names></name> <name><surname>Hajdas</surname> <given-names>I.</given-names></name> <name><surname>Suter</surname> <given-names>M.</given-names></name> <name><surname>Synal</surname> <given-names>H. A.</given-names></name><etal/></person-group> (<year>2010</year>). <article-title>On-line radiocarbon measurements of small samples using elemental analyzer and MICADAS gas ion source.</article-title> <source><italic>Radiocarbon</italic></source> <volume>52</volume> <fpage>1645</fpage>&#x2013;<lpage>1656</lpage>. <pub-id pub-id-type="doi">10.1017/S003382220005637X</pub-id></citation></ref>
<ref id="B111"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>S&#x00E1;nchez-Garc&#x00ED;a</surname> <given-names>L.</given-names></name> <name><surname>Vonk</surname> <given-names>J. E.</given-names></name> <name><surname>Charkin</surname> <given-names>A. N.</given-names></name> <name><surname>Kosmach</surname> <given-names>D.</given-names></name> <name><surname>Dudarev</surname> <given-names>O. V.</given-names></name> <name><surname>Semiletov</surname> <given-names>I. P.</given-names></name><etal/></person-group> (<year>2014</year>). <article-title>Characterisation of three regimes of collapsing arctic ice complex deposits on the SE Laptev sea coast using biomarkers and dual carbon isotopes.</article-title> <source><italic>Permafrost Periglac. Process.</italic></source> <volume>25</volume> <fpage>172</fpage>&#x2013;<lpage>183</lpage>. <pub-id pub-id-type="doi">10.1002/ppp.1815</pub-id></citation></ref>
<ref id="B112"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Sch&#x00E4;del</surname> <given-names>C.</given-names></name> <name><surname>Bader</surname> <given-names>M. K. F.</given-names></name> <name><surname>Schuur</surname> <given-names>E. A. G.</given-names></name> <name><surname>Biasi</surname> <given-names>C.</given-names></name> <name><surname>Bracho</surname> <given-names>R.</given-names></name> <name><surname>Capek</surname> <given-names>P.</given-names></name><etal/></person-group> (<year>2016</year>). <article-title>Potential carbon emissions dominated by carbon dioxide from thawed permafrost soils.</article-title> <source><italic>Nat. Clim. Change</italic></source> <volume>6</volume> <fpage>950</fpage>&#x2013;<lpage>953</lpage>. <pub-id pub-id-type="doi">10.1038/nclimate3054</pub-id></citation></ref>
<ref id="B113"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Sch&#x00E4;del</surname> <given-names>C.</given-names></name> <name><surname>Schuur</surname> <given-names>E. A. G.</given-names></name> <name><surname>Bracho</surname> <given-names>R.</given-names></name> <name><surname>Elberling</surname> <given-names>B.</given-names></name> <name><surname>Knoblauch</surname> <given-names>C.</given-names></name> <name><surname>Lee</surname> <given-names>H.</given-names></name><etal/></person-group> (<year>2014</year>). <article-title>Circumpolar assessment of permafrost C quality and its vulnerability over time using long-term incubation data.</article-title> <source><italic>Glob. Change Biol.</italic></source> <volume>20</volume> <fpage>641</fpage>&#x2013;<lpage>652</lpage>. <pub-id pub-id-type="doi">10.1111/gcb.12417</pub-id> <pub-id pub-id-type="pmid">24399755</pub-id></citation></ref>
<ref id="B114"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Schirrmeister</surname> <given-names>L.</given-names></name> <name><surname>Dietze</surname> <given-names>E.</given-names></name> <name><surname>Matthes</surname> <given-names>H.</given-names></name> <name><surname>Grosse</surname> <given-names>G.</given-names></name> <name><surname>Strauss</surname> <given-names>J.</given-names></name> <name><surname>Laboor</surname> <given-names>S.</given-names></name><etal/></person-group> (<year>2020</year>). <article-title>The genesis of Yedoma Ice complex permafrost &#x2013; grain-size endmember modeling analysis from Siberia and Alaska.</article-title> <source><italic>Quatern. Sci. J.</italic></source> <volume>69</volume> <fpage>33</fpage>&#x2013;<lpage>53</lpage>. <pub-id pub-id-type="doi">10.5194/egqsj-69-33-2020</pub-id></citation></ref>
<ref id="B115"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Schirrmeister</surname> <given-names>L.</given-names></name> <name><surname>Grigoriev</surname> <given-names>M. N.</given-names></name> <name><surname>Strauss</surname> <given-names>J.</given-names></name> <name><surname>Grosse</surname> <given-names>G.</given-names></name> <name><surname>Overduin</surname> <given-names>P. P.</given-names></name> <name><surname>Kholodov</surname> <given-names>A.</given-names></name><etal/></person-group> (<year>2018</year>). <article-title>Sediment characteristics of a thermokarst lagoon in the northeastern Siberian Arctic (Ivashkina Lagoon, Bykovsky Peninsula).</article-title> <source><italic>Arktos</italic></source> <volume>4</volume> <fpage>1</fpage>&#x2013;<lpage>16</lpage>. <pub-id pub-id-type="doi">10.1007/s41063-018-0049-8</pub-id></citation></ref>
<ref id="B116"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Schuur</surname> <given-names>E. A. G.</given-names></name> <name><surname>McGuire</surname> <given-names>A. D.</given-names></name> <name><surname>Grosse</surname> <given-names>G.</given-names></name> <name><surname>Harden</surname> <given-names>J. W.</given-names></name> <name><surname>Hayes</surname> <given-names>D. J.</given-names></name> <name><surname>Hugelius</surname> <given-names>G.</given-names></name><etal/></person-group> (<year>2015</year>). <article-title>Climate change and the permafrost carbon feedback.</article-title> <source><italic>Nature</italic></source> <volume>520</volume> <fpage>171</fpage>&#x2013;<lpage>179</lpage>. <pub-id pub-id-type="doi">10.1038/nature14338</pub-id> <pub-id pub-id-type="pmid">25855454</pub-id></citation></ref>
<ref id="B117"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Semiletov</surname> <given-names>I. P.</given-names></name> <name><surname>Pipko</surname> <given-names>I.</given-names></name> <name><surname>Gustafsson</surname> <given-names>&#x00D6;</given-names></name> <name><surname>Anderson</surname> <given-names>L. G.</given-names></name> <name><surname>Sergienko</surname> <given-names>V.</given-names></name> <name><surname>Pugach</surname> <given-names>S.</given-names></name><etal/></person-group> (<year>2016</year>). <article-title>Acidification of East Siberian Arctic Shelf waters through addition of freshwater and terrestrial carbon.</article-title> <source><italic>Nat. Geosci.</italic></source> <volume>9</volume> <fpage>361</fpage>&#x2013;<lpage>365</lpage>. <pub-id pub-id-type="doi">10.1038/NEGO2695</pub-id></citation></ref>
<ref id="B118"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Semiletov</surname> <given-names>I. P.</given-names></name> <name><surname>Shakhova</surname> <given-names>N. E.</given-names></name> <name><surname>Pipko</surname> <given-names>I. I.</given-names></name> <name><surname>Pugach</surname> <given-names>S. P.</given-names></name> <name><surname>Charkin</surname> <given-names>A. N.</given-names></name> <name><surname>Dudarev</surname> <given-names>O. V.</given-names></name><etal/></person-group> (<year>2013</year>). <article-title>Space-time dynamics of carbon and environmental parameters related to carbon dioxide emissions in the Buor-Khaya Bay and adjacent part of the Laptev Sea.</article-title> <source><italic>Biogeosciences</italic></source> <volume>10</volume> <fpage>5977</fpage>&#x2013;<lpage>5996</lpage>. <pub-id pub-id-type="doi">10.5194/bg-10-5977-2013</pub-id></citation></ref>
<ref id="B119"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Shakhova</surname> <given-names>N.</given-names></name> <name><surname>Semiletov</surname> <given-names>I.</given-names></name> <name><surname>Salyuk</surname> <given-names>A.</given-names></name> <name><surname>Yusupov</surname> <given-names>V.</given-names></name> <name><surname>Kosmach</surname> <given-names>D.</given-names></name> <name><surname>Gustafsson</surname> <given-names>O.</given-names></name></person-group> (<year>2010</year>). <article-title>Extensive methane venting to the atmosphere from sediments of the East Siberian Arctic Shelf.</article-title> <source><italic>Science</italic></source> <volume>327</volume> <fpage>1246</fpage>&#x2013;<lpage>1250</lpage>. <pub-id pub-id-type="doi">10.1126/science.1182221</pub-id> <pub-id pub-id-type="pmid">20203047</pub-id></citation></ref>
<ref id="B120"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Shakhova</surname> <given-names>N.</given-names></name> <name><surname>Semiletov</surname> <given-names>I.</given-names></name> <name><surname>Sergienko</surname> <given-names>V.</given-names></name> <name><surname>Lobkovsky</surname> <given-names>L.</given-names></name> <name><surname>Yusupov</surname> <given-names>V.</given-names></name> <name><surname>Salyuk</surname> <given-names>A.</given-names></name><etal/></person-group> (<year>2015</year>). <article-title>The East Siberian Arctic Shelf: towards further assessment of permafrost-related methane fluxes and role of sea ice.</article-title> <source><italic>Philos. Trans. R. Soc. A Math. Phys. Eng. Sci.</italic></source> <volume>373</volume> <issue>20140451</issue>. <pub-id pub-id-type="doi">10.1098/rsta.2014.0451</pub-id> <pub-id pub-id-type="pmid">26347539</pub-id></citation></ref>
<ref id="B121"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Smith</surname> <given-names>C. A. S.</given-names></name> <name><surname>Kennedy</surname> <given-names>C. E.</given-names></name> <name><surname>Hargrave</surname> <given-names>A. E.</given-names></name> <name><surname>McKenna</surname> <given-names>K. M.</given-names></name></person-group> (<year>1989</year>). <source><italic>Soil and Vegetation of Herschel Island, Yukon Soil Survey Report</italic></source>, <volume>Vol. 1</volume>. <publisher-loc>Ottawa, ON</publisher-loc>: <publisher-name>Land Resource Research Centre, Agriculture Canada</publisher-name>.</citation></ref>
<ref id="B122"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Sollins</surname> <given-names>P.</given-names></name> <name><surname>Spycher</surname> <given-names>G.</given-names></name> <name><surname>Glassman</surname> <given-names>C. A.</given-names></name></person-group> (<year>1984</year>). <article-title>Net nitrogen mineralization from light- and heavy-fraction forest soil organic matter.</article-title> <source><italic>Soil Biol. Biochem.</italic></source> <volume>16</volume> <fpage>31</fpage>&#x2013;<lpage>37</lpage>. <pub-id pub-id-type="doi">10.1016/0038-0717(84)90122-6</pub-id></citation></ref>
<ref id="B123"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Solomon</surname> <given-names>S. M.</given-names></name></person-group> (<year>2005</year>). <article-title>Spatial and temporal variability of shoreline change in the Beaufort-Mackenzie region, northwest territories, Canada.</article-title> <source><italic>Geo Mar. Lett.</italic></source> <volume>25</volume> <fpage>127</fpage>&#x2013;<lpage>137</lpage>. <pub-id pub-id-type="doi">10.1007/s00367-004-0194-x</pub-id></citation></ref>
<ref id="B124"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Spencer</surname> <given-names>R. G. M.</given-names></name> <name><surname>Mann</surname> <given-names>P. J.</given-names></name> <name><surname>Dittmar</surname> <given-names>T.</given-names></name> <name><surname>Eglinton</surname> <given-names>T. I.</given-names></name> <name><surname>McIntyre</surname> <given-names>C.</given-names></name> <name><surname>Holmes</surname> <given-names>R. M.</given-names></name><etal/></person-group> (<year>2015</year>). <article-title>Detecting the signature of permafrost thaw in Arctic rivers.</article-title> <source><italic>Geophys. Res. Lett. Res. Lett.</italic></source> <volume>42</volume> <fpage>2830</fpage>&#x2013;<lpage>2835</lpage>. <pub-id pub-id-type="doi">10.1002/2015GL063498</pub-id></citation></ref>
<ref id="B125"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Stein</surname> <given-names>R.</given-names></name> <name><surname>Macdonald</surname> <given-names>R. W.</given-names></name></person-group> (<year>2004</year>). <source><italic>The Arctic Organic Carbon Cycle: Present and Past.</italic></source> <publisher-loc>Berlin</publisher-loc>: <publisher-name>Springer</publisher-name>.</citation></ref>
<ref id="B126"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Stevenson</surname> <given-names>F. J.</given-names></name></person-group> (<year>1994</year>). <source><italic>Humus Chemistry: Genesis, Composition, Reactions.</italic></source> <publisher-loc>New York, NY</publisher-loc>: <publisher-name>John Wiley &#x0026; Sons</publisher-name>.</citation></ref>
<ref id="B127"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Strauss</surname> <given-names>J.</given-names></name> <name><surname>Schirrmeister</surname> <given-names>L.</given-names></name> <name><surname>Mangelsdorf</surname> <given-names>K.</given-names></name> <name><surname>Eichhorn</surname> <given-names>L.</given-names></name> <name><surname>Wetterich</surname> <given-names>S.</given-names></name> <name><surname>Herzschuh</surname> <given-names>U.</given-names></name></person-group> (<year>2015</year>). <article-title>Organic-matter quality of deep permafrost carbon - A study from Arctic Siberia.</article-title> <source><italic>Biogeosciences</italic></source> <volume>12</volume> <fpage>2227</fpage>&#x2013;<lpage>2245</lpage>. <pub-id pub-id-type="doi">10.5194/bg-12-2227-2015</pub-id></citation></ref>
<ref id="B128"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Suzuki</surname> <given-names>Y.</given-names></name> <name><surname>Kudoh</surname> <given-names>S.</given-names></name> <name><surname>Takahashi</surname> <given-names>M.</given-names></name></person-group> (<year>1997</year>). <article-title>Photosynthetic and respiratory characteristics of an Arctic ice algal community living in low light and low temperature conditions.</article-title> <source><italic>J. Mar. Syst.</italic></source> <volume>11</volume> <fpage>111</fpage>&#x2013;<lpage>121</lpage>. <pub-id pub-id-type="doi">10.1016/S0924-7963(96)00032-2</pub-id></citation></ref>
<ref id="B129"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Tanski</surname> <given-names>G.</given-names></name> <name><surname>Lantuit</surname> <given-names>H.</given-names></name> <name><surname>Ruttor</surname> <given-names>S.</given-names></name> <name><surname>Knoblauch</surname> <given-names>C.</given-names></name> <name><surname>Radosavljevic</surname> <given-names>B.</given-names></name> <name><surname>Strauss</surname> <given-names>J.</given-names></name><etal/></person-group> (<year>2017</year>). <article-title>Transformation of terrestrial organic matter along thermokarst-affected permafrost coasts in the Arctic.</article-title> <source><italic>Sci. Total Environ.</italic></source> <volume>581&#x2013;582</volume> <fpage>434</fpage>&#x2013;<lpage>447</lpage>. <pub-id pub-id-type="doi">10.1016/j.scitotenv.2016.12.152</pub-id> <pub-id pub-id-type="pmid">28088543</pub-id></citation></ref>
<ref id="B130"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Tanski</surname> <given-names>G.</given-names></name> <name><surname>Wagner</surname> <given-names>D.</given-names></name> <name><surname>Knoblauch</surname> <given-names>C.</given-names></name> <name><surname>Fritz</surname> <given-names>M.</given-names></name> <name><surname>Sachs</surname> <given-names>T.</given-names></name> <name><surname>Lantuit</surname> <given-names>H.</given-names></name></person-group> (<year>2019</year>). <article-title>Rapid CO2 release from eroding permafrost in seawater.</article-title> <source><italic>Geophys. Res. Lett.</italic></source> <volume>46</volume> <fpage>11244</fpage>&#x2013;<lpage>11252</lpage>. <pub-id pub-id-type="doi">10.1029/2019GL084303</pub-id></citation></ref>
<ref id="B131"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Vonk</surname> <given-names>J. E.</given-names></name> <name><surname>Gustafsson</surname> <given-names>O.</given-names></name></person-group> (<year>2013</year>). <article-title>Permafrost-carbon complexities.</article-title> <source><italic>Nat. Geosci.</italic></source> <volume>6</volume> <fpage>675</fpage>&#x2013;<lpage>676</lpage>. <pub-id pub-id-type="doi">10.1038/ngeo1937</pub-id></citation></ref>
<ref id="B132"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Vonk</surname> <given-names>J. E.</given-names></name> <name><surname>S&#x00E1;nchez-Garc&#x00ED;a</surname> <given-names>L.</given-names></name> <name><surname>Semiletov</surname> <given-names>I.</given-names></name> <name><surname>Dudarev</surname> <given-names>O.</given-names></name> <name><surname>Eglinton</surname> <given-names>T.</given-names></name> <name><surname>Andersson</surname> <given-names>A.</given-names></name><etal/></person-group> (<year>2010</year>). <article-title>Molecular and radiocarbon constraints on sources and degradation of terrestrial organic carbon along the Kolyma paleoriver transect. East Siberian Sea.</article-title> <source><italic>Biogeosciences</italic></source> <volume>7</volume> <fpage>3153</fpage>&#x2013;<lpage>3166</lpage>. <pub-id pub-id-type="doi">10.5194/bg-7-3153-2010</pub-id></citation></ref>
<ref id="B133"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Vonk</surname> <given-names>J. E.</given-names></name> <name><surname>S&#x00E1;nchez-Garc&#x00ED;a</surname> <given-names>L.</given-names></name> <name><surname>van Dongen</surname> <given-names>B. E.</given-names></name> <name><surname>Alling</surname> <given-names>V.</given-names></name> <name><surname>Kosmach</surname> <given-names>D.</given-names></name> <name><surname>Charkin</surname> <given-names>A.</given-names></name><etal/></person-group> (<year>2012</year>). <article-title>Activation of old carbon by erosion of coastal and subsea permafrost in Arctic Siberia.</article-title> <source><italic>Nature</italic></source> <volume>489</volume> <fpage>137</fpage>&#x2013;<lpage>140</lpage>. <pub-id pub-id-type="doi">10.1038/nature11392</pub-id> <pub-id pub-id-type="pmid">22932271</pub-id></citation></ref>
<ref id="B134"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Vonk</surname> <given-names>J. E.</given-names></name> <name><surname>Semiletov</surname> <given-names>I. P.</given-names></name> <name><surname>Dudarev</surname> <given-names>O. V.</given-names></name> <name><surname>Eglinton</surname> <given-names>T. I.</given-names></name> <name><surname>Andersson</surname> <given-names>A.</given-names></name> <name><surname>Shakhova</surname> <given-names>N.</given-names></name><etal/></person-group> (<year>2014</year>). <article-title>Preferential burial of permafrost-derived organic carbon in Siberian-Arctic shelf waters.</article-title> <source><italic>J. Geophys. Res. Oceans</italic></source> <volume>119</volume> <fpage>8410</fpage>&#x2013;<lpage>8421</lpage>. <pub-id pub-id-type="doi">10.1002/2014JC010261</pub-id></citation></ref>
<ref id="B135"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Vonk</surname> <given-names>J. E.</given-names></name> <name><surname>Tank</surname> <given-names>S. E.</given-names></name> <name><surname>Mann</surname> <given-names>P. J.</given-names></name> <name><surname>Spencer</surname> <given-names>R. G. M.</given-names></name> <name><surname>Treat</surname> <given-names>C. C.</given-names></name> <name><surname>Striegl</surname> <given-names>R. G.</given-names></name><etal/></person-group> (<year>2015</year>). <article-title>Biodegradability of dissolved organic carbon in permafrost soils and waterways: a meta-analysis.</article-title> <source><italic>Biogeosci. Discuss.</italic></source> <volume>12</volume> <fpage>8353</fpage>&#x2013;<lpage>8393</lpage>. <pub-id pub-id-type="doi">10.5194/bgd-12-8353-2015</pub-id></citation></ref>
<ref id="B136"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Walz</surname> <given-names>J.</given-names></name> <name><surname>Knoblauch</surname> <given-names>C.</given-names></name> <name><surname>B&#x00F6;hme</surname> <given-names>L.</given-names></name> <name><surname>Pfeiffer</surname> <given-names>E.-M.</given-names></name></person-group> (<year>2017</year>). <article-title>Regulation of soil organic matter decomposition in permafrost-affected Siberian tundra soils - Impact of oxygen availability, freezing and thawing, temperature, and labile organic matter.</article-title> <source><italic>Soil Biol. Biochem.</italic></source> <volume>110</volume> <fpage>34</fpage>&#x2013;<lpage>43</lpage>. <pub-id pub-id-type="doi">10.1016/j.soilbio.2017.03.001</pub-id></citation></ref>
<ref id="B137"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Ward</surname> <given-names>C. P.</given-names></name> <name><surname>Cory</surname> <given-names>R. M.</given-names></name></person-group> (<year>2016</year>). <article-title>Complete and partial photo-oxidation of dissolved organic matter draining permafrost soils.</article-title> <source><italic>Environ. Sci. Technol.</italic></source> <volume>50</volume> <fpage>3545</fpage>&#x2013;<lpage>3553</lpage>. <pub-id pub-id-type="doi">10.1021/acs.est.5b05354</pub-id> <pub-id pub-id-type="pmid">26910810</pub-id></citation></ref>
<ref id="B138"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Ward</surname> <given-names>R. D.</given-names></name></person-group> (<year>2020</year>). <article-title>Sedimentary response of Arctic coastal wetlands to sea level rise.</article-title> <source><italic>Geomorpholgy</italic></source> <volume>370</volume>:<issue>107400</issue>. <pub-id pub-id-type="doi">10.1016/j.geomorph.2020.107400</pub-id></citation></ref>
<ref id="B139"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Wegner</surname> <given-names>C.</given-names></name> <name><surname>Bennett</surname> <given-names>K. E.</given-names></name> <name><surname>de Vernal</surname> <given-names>A.</given-names></name> <name><surname>Forwick</surname> <given-names>M.</given-names></name> <name><surname>Fritz</surname> <given-names>M.</given-names></name> <name><surname>Heikkila</surname> <given-names>M.</given-names></name><etal/></person-group> (<year>2015</year>). <article-title>Variability in transport of terrigenous material on the shelves and the deep Arctic Ocean during the Holocene.</article-title> <source><italic>Polar Res.</italic></source> <volume>34</volume> <fpage>1</fpage>&#x2013;<lpage>19</lpage>. <pub-id pub-id-type="doi">10.3402/polar.v34.24964</pub-id></citation></ref>
<ref id="B140"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Welte</surname> <given-names>D. H.</given-names></name> <name><surname>Waples</surname> <given-names>D. W.</given-names></name></person-group> (<year>1973</year>). <article-title>&#x00DC;ber die Bevorzugung geradzahliger n-Alkane in Sedimentgesteinen.</article-title> <source><italic>Naturwissenschaften</italic></source> <volume>60</volume> <fpage>516</fpage>&#x2013;<lpage>517</lpage>.</citation></ref>
<ref id="B141"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Wild</surname> <given-names>B.</given-names></name> <name><surname>Gentsch</surname> <given-names>N.</given-names></name> <name><surname>Capek</surname> <given-names>P.</given-names></name> <name><surname>Di&#x00E1;kov&#x00E1;</surname> <given-names>K.</given-names></name> <name><surname>Alves</surname> <given-names>R. J. E.</given-names></name> <name><surname>B&#x00E1;rta</surname> <given-names>J.</given-names></name><etal/></person-group> (<year>2016</year>). <article-title>Plant-derived compounds stimulate the decomposition of organic matter in arctic permafrost soils.</article-title> <source><italic>Sci. Rep.</italic></source> <volume>6</volume>:<issue>25607</issue>. <pub-id pub-id-type="doi">10.1038/srep25607</pub-id> <pub-id pub-id-type="pmid">27157964</pub-id></citation></ref>
<ref id="B142"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Wild</surname> <given-names>B.</given-names></name> <name><surname>Schnecker</surname> <given-names>J.</given-names></name> <name><surname>Alves</surname> <given-names>R. J. E.</given-names></name> <name><surname>Barsukov</surname> <given-names>P.</given-names></name> <name><surname>B&#x00E1;rta</surname> <given-names>J.</given-names></name> <name><surname>&#x010C;apek</surname> <given-names>P.</given-names></name><etal/></person-group> (<year>2014</year>). <article-title>Input of easily available organic C and N stimulates microbial decomposition of soil organic matter in arctic permafrost soil.</article-title> <source><italic>Soil Biol. Biochem.</italic></source> <volume>75</volume> <fpage>143</fpage>&#x2013;<lpage>151</lpage>. <pub-id pub-id-type="doi">10.1016/j.soilbio.2014.04.014</pub-id> <pub-id pub-id-type="pmid">25089062</pub-id></citation></ref>
<ref id="B143"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Wolf-Gladrow</surname> <given-names>D. A.</given-names></name> <name><surname>Zeebe</surname> <given-names>R. E.</given-names></name> <name><surname>Klaas</surname> <given-names>C.</given-names></name> <name><surname>K&#x00F6;rtzinger</surname> <given-names>A.</given-names></name> <name><surname>Dickson</surname> <given-names>A. G.</given-names></name></person-group> (<year>2007</year>). <article-title>Total alkalinity: the explicit conservative expression and its application to biogeochemical processes.</article-title> <source><italic>Mar. Chem.</italic></source> <volume>106</volume> <fpage>287</fpage>&#x2013;<lpage>300</lpage>. <pub-id pub-id-type="doi">10.1016/j.marchem.2007.01.006</pub-id></citation></ref>
<ref id="B144"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Wolter</surname> <given-names>J.</given-names></name> <name><surname>Lantuit</surname> <given-names>H.</given-names></name> <name><surname>Fritz</surname> <given-names>M.</given-names></name> <name><surname>Macias-Fauria</surname> <given-names>M.</given-names></name> <name><surname>Myers-Smith</surname> <given-names>I.</given-names></name> <name><surname>Herzschuh</surname> <given-names>U.</given-names></name></person-group> (<year>2016</year>). <article-title>Vegetation composition and shrub extent on the Yukon coast, Canada, are strongly linked to ice-wedge polygon degradation.</article-title> <source><italic>Polar Res.</italic></source> <volume>35</volume>:<issue>27489</issue>. <pub-id pub-id-type="doi">10.3402/polar.v35.27489</pub-id></citation></ref>
<ref id="B145"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Zolkos</surname> <given-names>S.</given-names></name> <name><surname>Tank</surname> <given-names>S. E.</given-names></name> <name><surname>Kokelj</surname> <given-names>S. V.</given-names></name></person-group> (<year>2018</year>). <article-title>Mineral weathering and the permafrost carbon-climate feedback.</article-title> <source><italic>Geophys. Res. Lett.</italic></source> <volume>45</volume> <fpage>9623</fpage>&#x2013;<lpage>9632</lpage>. <pub-id pub-id-type="doi">10.1029/2018GL078748</pub-id></citation></ref>
</ref-list></back>
</article>
