ORIGINAL RESEARCH article
Front. Mar. Sci.
Sec. Marine Biogeochemistry
Carbon in an Arctic fjord: sea-ice carbon transformations, and CO₂ linkages
Provisionally accepted
- 1University of Stirling, Stirling, United Kingdom
- 2University of Stirling Division of Biological and Environmental Sciences, Stirling, United Kingdom
- 3Norsk Polarinstitutt, Tromsø, Norway
- 4Havforskningsinstituttet Avdeling Tromso, Tromsø, Norway
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The biogeochemical processes underlying carbon cycling in Arctic coastal systems are rapidly evolving due to intensified ice loss. This study examines the distinct contributions of dissolved organic carbon (DOC) and particulate carbon from sea-ice in Kongsfjorden, Svalbard, focusing on the optical characteristics of coloured dissolved organic matter (CDOM) to trace its fate. Our results reveal that sea-ice melt delivers a complex mixture: specific types of CDOM and a dominant load of total particulate carbon (TPC) that was identified as being primarily particulate inorganic carbon (PIC). The fate of the dissolved fraction was clearly traced by gaussian decomposition. Sea-ice delivered nitrogen-rich organic components, creating spatial hotspots of aCDOM275 at the inner-and of aCDOM330 at the outer-most site with a strong correlation with CO2. At the surface, photodegradation breaks down high-molecular-weight (HMW) (low S275-295) dissolved organic matter (DOM) into low-molecular-weight (LMW) fractions (high S275-295). Below the surface, microbial degradation further transforms this organic carbon, promoting remineralisation processes and releasing dissolved inorganic carbon (DIC) and CO2. Higher N:P and Si:P ratios and nutrients in these layers indicated enrichment by meltwater (sea-ice/glacial), and microbial OM degradation supported by shifts in CDOM spectral properties (SR, S275-295, S350-400) and higher CO2. In contrast, the PIC-dominated TPC pool was decoupled from these biological transformations. Given the accelerating rate of Arctic warming, the impacts of sea-ice and glacial melting on carbon dynamics in fjords like Kongsfjorden are likely to intensify, with potential positive feedback in the Arctic.
Keywords: dissolved organic carbon, Total particulate carbon, coloured dissolved organic carbon, Sea-ice, Fjord, Kongsfjorden
Received: 18 Aug 2025; Accepted: 28 Oct 2025.
Copyright: © 2025 Aguilar Vega, Fransson, Melissa, Washbourne and Spyrakos. 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) or licensor 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.
* Correspondence: Ximena Aguilar Vega, x.a.aguilar.vega@stir.ac.uk
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