Edited by: Laura Lorenzoni, University of South Florida, Tampa, United States
Reviewed by: Frank Dehairs, Vrije Universiteit Brussel, Belgium; Mathieu Ardyna, Stanford University, United States; Matthew Long, National Center for Atmospheric Research (UCAR), United States
†These authors have contributed equally to this work
This article was submitted to Ocean Observation, a section of the journal Frontiers in Marine Science
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The Southern Ocean is disproportionately important in its effect on the Earth system, impacting climatic, biogeochemical, and ecological systems, which makes recent observed changes to this system cause for global concern. The enhanced understanding and improvements in predictive skill needed for understanding and projecting future states of the Southern Ocean require sustained observations. Over the last decade, the Southern Ocean Observing System (SOOS) has established networks for enhancing regional coordination and research community groups to advance development of observing system capabilities. These networks support delivery of the SOOS 20-year vision, which is to develop a circumpolar system that ensures time series of key variables, and delivers the greatest impact from data to all key end-users. Although the Southern Ocean remains one of the least-observed ocean regions, enhanced international coordination and advances in autonomous platforms have resulted in progress toward sustained observations of this region. Since 2009, the Southern Ocean community has deployed over 5700 observational platforms south of 40°S. Large-scale, multi-year or sustained, multidisciplinary efforts have been supported and are now delivering observations of essential variables at space and time scales that enable assessment of changes being observed in Southern Ocean systems. The improved observational coverage, however, is predominantly for the open ocean, encompasses the summer, consists of primarily physical oceanographic variables, and covers surface to 2000 m. Significant gaps remain in observations of the ice-impacted ocean, the sea ice, depths >2000 m, the air-ocean-ice interface, biogeochemical and biological variables, and for seasons other than summer. Addressing these data gaps in a sustained way requires parallel advances in coordination networks, cyberinfrastructure and data management tools, observational platform and sensor technology, two-way platform interrogation and data-transmission technologies, modeling frameworks, intercalibration experiments, and development of internationally agreed sampling standards and requirements of key variables. This paper presents a community statement on the major scientific and observational progress of the last decade, and importantly, an assessment of key priorities for the coming decade, toward achieving the SOOS vision and delivering essential data to all end-users.
The Southern Ocean has a profound influence on the Earth system (e.g.,
The Southern Ocean Observing System (SOOS) was established in 2011 as a partnership between the Scientific Committee on Antarctic Research (SCAR) and the Scientific Committee on Oceanic Research (SCOR) to enhance delivery of the data required to reduce these uncertainties. This collaboration followed years of international discussions that were distilled and published in the OceanObs’09 White Papers (
The role of the Southern Ocean in the planet’s heat and freshwater balance.
The stability of the Southern Ocean overturning circulation.
The role of the ocean in the stability of the Antarctic Ice Sheet and its future contribution to sea-level rise.
The future and consequences of Southern Ocean carbon uptake.
The future of Antarctic sea ice.
Impacts of global change on Southern Ocean ecosystems.
Southern Ocean Observing System involves many nations, significant resources, and multiple end-users, which makes its 20-year vision critical for enabling long-term strategic planning and preventing mission drift (
Schematic of a cyberinfrastructure-based vision for SOOS (
Achieving such a vision requires parallel advances in coordination networks, cyberinfrastructure and data management tools, observational platform and sensor technology, platform interrogation and data-transmission technologies, modeling frameworks, and internationally agreed sampling requirements of key variables. Toward this end, SOOS is working with the broader community to: develop regional networks for integration of international observational field activities (
Map of the five Regional Working Groups developed by SOOS to integrate the existing observational efforts in a region and facilitate efforts to address key gaps in observational coverage. The regions are based on the natural areas of focus for nations working in the Southern Ocean and facilitate regional coordination in (1) scientific information exchange, (2) technology transfer/collaboration, (3) standardization of measurements, and (4) sharing of data. The Partner Observing Area is a region not presently covered by a working group. In the interim, the SOOS Scientific Steering Committee will maintain oversight of the observational coverage of this region to ensure requirements are met. Base map data from ESRI, GARMIN, GEBCO, NOAA NGDC, and others.
SOOSmap is an interactive webmap that allows users to explore circumpolar datasets. It was developed for SOOS by EMODnet Physics and enables users to search within different spatial and temporal filters, and to select different platforms, variables, and data layers. SOOSmap is an open access and provides direct data downloads where possible (
DueSouth is the Database of Upcoming Expeditions to the Southern Ocean and is a coordination tool that enables users to find out which expeditions (e.g., voyages, flights, traverses) are planned for future field seasons, and what observational projects are funded to take place on each expedition. It is developed and maintained for SOOS by the Australian Antarctic Data Centre.
Since 2009, the number of Southern Ocean observations collected has increased considerably, enabled by rapid progress in the development, capability, and use of autonomous and robotic systems. SOOS has supported this progress by defining and promoting the vision around the systems that are needed, and also by endorsing and supporting the funding acquisition by various nations’ investigators [e.g., Research of Ocean-ice BOundry InTeraction and Change around Antarctica (ROBOTICA)
The implementation of these programs over the last decade has enabled the community to make significant statements on the state of the Southern Ocean and how it is changing.
The Southern Ocean is warming faster than any other sector of the global ocean (
Increases in the westerly winds overlying the ACC are hypothesized to result in an increased net meridional overturning circulation (MOC) associated with enhanced poleward transport of heat by mesoscale eddies and a stronger equatorward return Ekman transport at the surface (
While the waters north of the SAF have warmed significantly, the sea-surface waters south of the ACC core and Polar Front have changed less than the global sea-surface temperature trend (0.02°C/decade cf. 0.08°C/decade since 1950). This north–south temperature trend contrast reflects the continual renewal of the surface waters south of the Polar Front from below by old Circumpolar Deep Water (CDW) that has yet been largely unmodified by anthropogenic influences (
The Southern Ocean is also freshening (
The Antarctic Ice Sheet is the greatest source of uncertainty in projections of future sea level (
Although the largest ice shelves (Ross, Filchner-Ronne, and Amery) have remained within their observed historical ranges, many smaller ice shelves have thinned, decreased in extent or disintegrated, leading to increased rates of discharge of grounded inland ice to the ocean. Large changes have occurred in the Amundsen Sea Embayment, where warm salty deep water intrudes on the continental shelf (
Recent observations indicate that other parts of the Antarctic Ice Sheet are equally vulnerable, such as the Filchner-Ronne Ice Shelf (
The Southern Ocean is Earth’s largest CO2 sink (
Much uncertainty remains regarding the Southern Ocean’s role in global carbon cycling due largely to data gaps, particularly in non-summer seasons and coastal regions (
Estimating Southern Ocean annual net community production (ANCP) is important for understanding the role of the biological pump in sequestering anthropogenic CO2 (
Antarctic coastal regions, such as the WAP, are highly productive yet spatially and temporally variable. Long-term, multi-national observations have revealed the interconnectivity of climate oscillations and physical forcing mechanisms (wind-stress, temperature) in controlling WAP seasonal sea-ice coverage, seasonality, and properties (
Considerable progress has been made since
Sea ice influences surface albedo and oceanic overturning circulation; affects stratification and properties of upper ocean; regulates heat, momentum, and gas transfer between the ocean and atmosphere; protects and stabilizes certain ice shelves (
While sea-ice extent and concentration have been quantified to reasonable accuracy from space since 1979, more robust statements on the nature of sea-ice changes and their drivers (including their regional and seasonal dependence) are impeded by a lack of observations and process understanding. Atmosphere and ocean forcing are poorly observed and understood; sea-ice thickness (and volume) are poorly known, as is the distribution of snow-cover depth (
The Southern Ocean, with its sea-ice cover, modulates nearly all ecosystems and life in Antarctica. While birds and some mammals breed on land, they all feed in the ocean. Changing air temperatures, wind patterns, sea ice, ocean frontal areas, and water-mass circulation therefore have profound and regionally specific effects on biota, impacting the adaptation capacity and survival of individual species, and promoting cascading effects throughout the ecosystem (
At the base of the food web, trends in phytoplankton differ among areas and latitudes.
For first-order phytoplankton consumers, zooplankton, and micronekton (those organisms in the size range between zooplankton and higher predators – notably krill, and small mid-water fishes and squids), accurate biomass estimations remain a major challenge. A recent modeling effort (
Top predators are excellent sentinels of change, as their species composition, demography, behavior, and diet reflect the community structure (
The combined implications of changes across multiple trophic levels for the structure and function of Southern Ocean ecosystems are not well understood, and will require coordinated observations and modeling to resolve (see the sections “Assessing Status and Trends of Key Southern Ocean Taxa” and “Southern Ocean Modelling progress and priorities”).
The next 10 years will see a step-change in the delivery of integrated, multidisciplinary Southern Ocean data. The SOOS Regional Working Groups and other networks developed over the last few years will become well-established, and will work with the community to design regional observing systems to collect sustained data and deliver them to all end-users. Importantly, the systems designed will need to be flexible, to take advantage of sensor and platform developments, new networks, funding or infrastructures, and to ensure continued impact of the data in addressing the most pressing issues for society. Toward this end, regular community review and updating of the scientific drivers of the observing system will be essential.
The SOOS Science Themes have provided clear focus for SOOS’s activities over the last decade, and in many instances, remain priorities for the coming decade of observations. Taking into account the progress of the community in delivering knowledge relevant to those themes (sections “Themes 1 and 2: The Role of the Southern Ocean in the Planet’s Heat and Freshwater Balance; and the Stability of the Southern Ocean Overturning Circulation,” “Theme 3: The Role of the Ocean in the Stability of the Antarctic Ice Sheet and Its Future Contribution to Sea-Level Rise,” “Theme 4: The Future and Consequences of Southern Ocean Carbon Uptake,” “Theme 5: The Future of Antarctic Sea Ice,” and “Theme 6: Impacts of Global Change on Southern Ocean Ecosystems”), the Southern Ocean community has identified eight key issues of focus for the coming decade. These issues are identified as major data bottlenecks in addressing the six themes, and are introduced in the following sections.
Conspicuous signals of climate change have been observed in Antarctic Bottom Water (AABW) including warming (
A schematic of the observational platforms required to observe the AABW formation.
These processes involve large-scale physics to meso- and submeso-scale physics (e.g.,
Southern Ocean
In 2015, the SOOS community identified fluxes as a priority observation gap, resulting in the development of the SOOS Southern Ocean Air-Sea Flux (SOFLUX
The key priority for the coming decade is to obtain more
Schematic of the key elements of a Southern Ocean air-sea flux observing system in order to reduce uncertainties in air-sea and air-sea-ice fluxes of heat, momentum, freshwater, and carbon (section “Reducing Uncertainties in Air-Sea and Air-Sea-Ice Fluxes of Heat, Momentum, Freshwater, and Carbon”). The optimal observing system would include buoys
Drivers of ice-shelf melt are poorly understood (
A schematic of the integrated system of observational platforms required to determine the contribution of oceanic heat to ice-shelf melt for a generic ice-shelf configuration. An integrated system to observe the processes important for grounding line retreat and basal melt consists of three main components. Firstly, observing how ocean currents approach and exit the ice shelf cavity, achieved by a combination of ship-based observations, such as hydrographic sections
Increased use of Autonomous Phase Sensitive Radars (ApRES;
To constrain numerical ocean and ice-sheet models, high resolution bathymetry on the continental shelves and within ice-shelf cavities, observations of ice-shelf draft, basal topography and roughness, and ocean observations that resolve the seasonal and intra-annual water mass and current variability are required. Increased use of autonomous technologies, long-range missions, improved under-ice navigation, and satellite transmission of the data will decrease the effort and cost involved in monitoring the transport of ocean heat toward the ice shelf bases.
The Partnership for Observation of the Global Oceans (POGO) has supported a SOOS working group Observing and Understanding the ocean below Antarctic Sea Ice and Ice Shelves (OASIIS
Although climate models include sea-ice components, they exhibit low skill in simulating observed Antarctic sea-ice properties and their spatio-temporal variability, i.e., seasonality, extent, concentration, and thickness (
Schematic of the platforms required to observe key sea-ice processes toward capturing circumpolar sea-ice variability (section “Toward a Better Understanding of Processes Controlling Antarctic Sea-Ice Variability and Change”) and deriving sea-ice thickness and volume (section “Observing Sea-Ice Thickness and Volume”). Due to the remoteness, vastness, and hostile conditions of the sea-ice zone, autonomous platforms will be crucial. They include high-resolution
Of high priority are gap-filling, multi-disciplinary
Satellite remote sensing – calibrated and validated by targeted
The two most important reasons for not being able to obtain accurate estimates of circum-Antarctic sea-ice thickness (
Improved observations of snow-depth distribution will require sustained and much broader deployment of snow-depth and ice mass balance stations/buoys (IMBs) that capture sufficient spatial and temporal variability to evaluate satellite and modeled snow-depth products. Increased use of airborne, and particularly unmanned aerial systems (UASs), are needed to provide broader-scale snow distributions and to extend radar-derived snow-thickness estimates from NASA’s Operation IceBridge mission to other regions and seasons (
To develop and validate ice-thickness products (e.g., from ICESat-2 and CryoSat-2), long-range, long-endurance AUVs (section “Priorities for Future Observational Technologies”) or long-range aerial sampling (i.e., EMBird) will also be needed. Traditional aerial platforms, UASs, and AUVs are critical to both extend traditional
Additionally, wider networks of IMBs are required to provide crucial data for evaluation of satellite-derived ice-thickness products. More extensive drifting buoy networks are also critical in the sea-ice zone to evaluate and improve reanalysis products (which are key to understanding the drivers of sea-ice variability) and are much more sparsely deployed than in the Arctic. Ice-tethered and under-ice floats (SOCCOM and ice-capable Argo) can help determine coupling between ice production and upper-ocean properties. At present, few floats are deployed under sea ice, and almost no ice-tethered sensors have yet been deployed. Lastly, drifting buoy networks provide high-resolution deformation data. This is essential to evaluating satellite-based deformation products that have more limited temporal resolution.
To constrain the Southern Ocean’s biogeochemical cycles, observations of oxygen, nutrients, dissolved inorganic carbon (DIC), dissolved organic carbon (DOC), transient tracers (e.g., CFCs), particulate organic carbon, and ocean-color measurements are a priority. Stable isotope measurements of nitrate, as well as DIC and silicic acid, are becoming powerful tools for constraining past and present biogeochemical processes and ocean circulation, and substantial datasets are accumulating across the Southern Ocean over the annual cycle (e.g.,
Components of an optimal observing system to constrain and quantify biogeochemical cycling processes in the Southern Ocean. New methodologies such as biogeochemical sensors deployed on SOCCOM
Despite significant progress in new technologies for biogeochemical observations, recent studies indicate that at least 100 Biogeochemical-Argo floats (BGC Argo) are needed to detect climate-scale changes in air-sea CO2 fluxes and Southern Ocean carbon and heat content (
Central to the Southern Ocean carbon cycle are the trace metals required for biological activity, with the most important being iron (e.g.,
An ongoing challenge in observing ecosystems is that key processes and major components are difficult or impossible to observe directly, and uncertainties around indirect observation methods are not well characterized. This is true for important processes and rates – such as predator–prey interactions, consumption and energy use, and growth rates – and also for estimating abundance and biomass of many key taxa (see section “Assessing Status and Trends of Key Southern Ocean Taxa”). Ecosystem EOVs (eEOVs) provide a mechanism to address these challenges (section “Conclusion and Recommendations”) and models are also important in integrating, contextualizing, and optimizing observations (section “Southern Ocean Modelling”).
Improved data streams that constrain biological energy pathways by better characterizing the transfer of mass through food webs, into carbon export, and into fish stocks are a priority to inform Southern Ocean ecosystem modeling, assessment, and management (
Major biological energy pathways by which energy moves from primary producers to higher trophic levels in Southern Ocean ecosystems (integrated across seasons and across open water and sea-ice environments). These pathways include the well-studied Krill food-chain (yellow), as well as less well-studied pathways via small fish and squid (green), and potentially salps (purple). The relative dominance of these pathways underpins ecosystem structure and function and the provision of services such as fisheries (blue hooks) and carbon sequestration (white dotted arrow). However, these pathways and the factors that determine their relative dominance in space and time are not well resolved. Targeted observing effort will be required to fill this knowledge gap.
Rapid development of telemetry and remote-sensing technologies are yielding increasingly rich observational datasets for taxa at the bottom and top of Southern Ocean food webs (i.e., phytoplankton and predators). Mid-trophic level groups, however, represent a major data gap due to a lower observing effort and uncertainties around primary observing methods: nets and acoustic backscatter (
Identifying the drivers of changes in abundance requires information on foraging behavior and tactics, which need to be integrated with data on the relevant biophysical factors. Changes in diet inferred from stomach flushing (
Other important gaps for biological observations that represent opportunities where the “value” of observation effort can be maximized include:
Observations from under sea ice and fast ice (especially measures of under-ice production and habitat characteristics);
Data on winter ecology or year-round studies;
Co-located (and co-incident) sampling of multiple ecosystem components (e.g., net sampling, acoustics, profiles, predator observations); and
System-level structural knowledge (i.e., measures of relative biomass of key taxa, links, and flux rates; see the section “Constraining Biological Energy Pathways”).
Schematic illustration of the observation and models required to resolve key uncertainties regarding the impacts of global change on Southern Ocean ecosystems (adapted from
The ocean and climate modeling community has achieved great progress in simulating the Southern Ocean during the last 10 years (see
Past and present freshwater input from ice-shelf melt is not well-constrained by observations, leading to a wide range of possible values used in global climate model studies of impacts on sea ice, water-mass formation, and overturning circulation (e.g.,
Recent modeling intercomparison studies have highlighted the pervasive biases and uncertainties in Southern Ocean dynamics and future projections (e.g.,
Heat and freshwater fluxes are responsible for the formation of Antarctic Intermediate Water (AAIW) and Sub-Antarctic Mode Water (SAMW), constituting the upper limb of the MOC (
Southern Ocean circulation, and heat and carbon uptake, are not only dependent on wind and buoyancy forcing, but also on isopycnal and diapycnal mixing, eddies, and topographic features. Mesoscale mixing is ubiquitous in the ocean, and plays a fundamental role in setting the overturning circulation, water-mass formation, and transport of tracers in the Southern Ocean. An accurate parameterization of mesoscale eddy mixing is a pressing challenge for the global ocean modeling community, and much work has been devoted to improving its representation in coarse-resolution models. For example, the eddy diffusivity has been related to the eddy kinetic energy derived through satellite altimetry. However, not only an estimate for the mean value is needed, but also its sensitivity to changes in forcing and interannual variability is crucial for properly representing mesoscale mixing processes and their effects on circulation and transport of tracers (e.g.,
Presently, vertical mixing for all these mechanisms is parameterized in ocean and climate models. Some of the parameterizations reproduce the wind-generated upper mixed-layer depth well, whereas others overmix the water column (
Ecosystem models are essential for integrating and contextualizing ecosystem observations, identifying how changes will affect ecosystems and the services they provide (
Common frameworks for ecosystem modeling include:
Population, growth, and habitat models for individual species (autecological models), focused on understanding how focal species respond to environmental conditions and external drivers such as harvest and bycatch (e.g., stock assessment models).
Nutrient–phytoplankton–zooplankton–detritus models focused on understanding lower trophic level dynamics in response to physical drivers;
Network models, representing linkages among components of ecosystems (synecological models) such as parts of the food web (functional groups and/or species), physical ecosystem components, and human activities.
International coordination of Southern Ocean ecosystem modeling is achieved through the Integrating Climate and Ecosystem Dynamics (ICED) subprogram of Integrating Marine Biosphere Research (IMBeR;
Southern Ocean food-web models are currently oriented around krill (
Ecosystem modeling capacity is currently limited by a lack of fit-for-purpose models and methods to evaluate the representativeness of models under development (i.e., model skill). This is due to difficulties in assembling data for difficult-to-observe parts of the ecosystem (section “Assessing Status and Trends of Key Southern Ocean Taxa”) and for trophic relations and rate parameters (section “Constraining Biological Energy Pathways”). Consolidating and comparing diets are a priority (
A core objective of SOOS is to ensure sustained delivery of the fundamental observations that meet the majority of stakeholder requirements. In the same way that the global network of meteorological stations provides end-users with a foundation of standardized observations around which to build specific requirements, SOOS will work with the broader Southern Ocean community to develop regionally defined, quantified sampling targets defining which observations are needed, where, how, and when. This will not only ensure base-level time series of key variables, but will support funders in identifying the observations that will deliver the greatest impact to the highest number of end-users. In combination with parallel efforts within the international community (e.g., through the Global Ocean Observing System
Ecosystem EOVs are the least developed in any observing system. Significant progress has been made in defining the process and criteria for determining eEOVs for the Southern Ocean (
The Southern Ocean Observing System has developed an Observing System Design Working Group to advance the knowledge and tools used in designing optimal observing systems. These tools, known as Observing System Simulation Experiments (OSSEs), are used to estimate the value of ocean observations, with respect to how well they constrain the goals of the observing system. Observing system design evaluation entails subsampling a realistic model solution and determining the ability to then reconstruct this model solution (e.g.,
Having a nature run with minimal omission errors allows accurate assessment of the observing system design and mapping method. It builds confidence in estimates of the observing system design and its skill in meeting the goals. Global ocean models are now being run with 2 km resolution in the Southern Ocean and appear to capture the internal wave spectrum (
Tools exist to design and prioritize the observing system. These are primarily based on model statistics (e.g.,
Given the size, complexity, operational cost, and harsh conditions, a broad suite of technologies is required to observe the Southern Ocean. The biggest driver of technology development is the urgent need to address the spatio-temporal data gaps in traditional ship-based sampling, and the last decade has seen significant progress on this front. Augmenting ship-based observations with satellite-sensor technology, autonomous platforms, and fixed assets such as moorings, has made a step-change in our observational capabilities (
Autonomous underwater vehicles have experienced strong growth in Antarctic science applications over the last two decades, operating under ice shelves and sea ice to collect otherwise inaccessible ocean and ice data. The UK’s National Oceanographic Centre’s Autosub group was the first to conduct AUV missions beneath sea ice (
Profiling floats have revolutionized sampling of the Southern Ocean (coordinated through the global Argo program), but the coverage of 1 float per 3 degrees is well behind the global average, with large gaps particularly south of 60°S and for >2000 m depth everywhere. In the coming decade, we expect the under-ice domains to be addressed but technological challenges related to fixing positioning and communication under the ice will need to improve, for example, through expansion of sound sources such as RAFOS. Deployment of deep Argo floats will close the data gap for depths >2000 m, and new “bottom drifters” (
Tagged marine animals, namely seals, have provided significant complementary datasets to the Argo program for temperature–salinity, and most recently fluorescence, from around the Antarctic margin and seasonal sea-ice zone. This technology has provided crucial winter and under-ice observations that could not be otherwise collected (
Underwater gliders now provide significant observations for the upper 1000 m at high spatio-temporal resolution and for multiple months at a time. They have been deployed over all parts of the Southern Ocean, including the ACC (
The use of UAS/drones for atmospheric (
Advances in moored platforms have been less broadly cited, but promising developments include bottom landers, such as the cheap, soccer-ball sized, ice-resistant, anchor-weighted “T-pop” buoys deployed to depths of 6000 m. Dropped from a ship, ice, or helicopter, they measure temperature and pressure for several years before surfacing and relaying the data via satellite. T-pops were successfully deployed by Sweden in the Amundsen Sea in 2016. Further, the newly developed ApRES instruments (coordinated through the NECKLACE program) collect time series of melt rates from point locations and complement the satellite-derived maps of melt rates that are now becoming available.
In addition to new platforms, a wide range of physical, chemical, and biological sensors are rapidly maturing. Advances in bio-acoustic technologies – both on ships and other platforms – will be critical to resolving uncertainties around the abundance and biomass of key mid-trophic-level taxa (
Along with new technologies, observational coverage can be enhanced using existing technology through more efficient use of resources. Although industry-based shipping in the Southern Ocean is marginal, fishing and tourism are growing industries with regular trips and, in many cases, the capability and interest to support observational activities. Additionally, station resupply voyages rarely operate underway observations without specific research requests, which, if coordinated, could provide a step-wise enhancement of observational coverage. The installation of sensors such as flux towers, multibeam echo sounders, standardized camera systems, snow radar, and electromagnetic induction sensors are important systems that could be installed on all vessels to greatly enhance spatial coverage. The GOOS Ship Of Opportunity Program (SOOP)
The international data-science landscape has changed significantly over the last decade, with the development of new data tools and an unprecedented increase in both the volume and diversity of data; presenting both opportunity and challenges. A particular challenge for SOOS is to link the science and data communities associated with National Antarctic Programs (NAPs) to the broader oceanographic community. The SOOS data system must leverage existing efforts, thus SOOS is working with other data initiatives to develop tools that bring together these efforts, to serve this thematically broad but regionally focused community.
Enhanced observations of the Southern Ocean will be of limited value if the data (
The SOOS data ecosystem (
A SOOS-centric view of the data ecosystem. Components that do not exist yet are denoted with dashed lines.
Southern Ocean Observing System is partnering with Antarctic data management organizations to deliver relevant gridded datasets (
Standardized datasets, such as those delivered through SOOSmap, require significant effort and for many data types the only practicable way to provide access is through comprehensive metadata discovery tools. At present, there are more than 70 metadata catalogs that contain SOOS-relevant data records (
This suite of tools will support the Southern Ocean community to add value to raw datasets (
All aspects of this data strategy require adequate and sustained funding, and given recent issues with sustained funding of data products, SOOS has identified core values for how community tools should be developed, including using free and open source software where available; not duplicating efforts; and creating a sense of community ownership so that the tools can survive changes in funding environments. Collectively, the SOOS ecosystem enables sharing and accessing data while being adaptable to the needs, varying levels of standardization, and patterns of IT use among the disciplines that comprise SOOS. As the global data management community further develops tools to make data more FAIR, the mix of tools in the SOOS data vision will allow its community to adapt to these changes.
The success of SOOS will ultimately be determined by the delivery of sustained observations to end-users, which include scientists, policy makers, and industry. This requires significant efforts to ensure an integrated and coordinated approach.
Unique to the Southern Ocean, the Antarctic Treaty provides a framework within which the use of Antarctic resources and services can be monitored and managed. Because of this, all users of the Southern Ocean (south of 60°S) are obligated to record their activities and monitor their impact. This requires sustained observation of environmental variables and transfer of data into knowledge and statements of impact or change. This requirement has supported the development of coordinating bodies who manage specific aspects of program monitoring requirements.
Ecosystem-based management approaches to regulate fisheries activity, for example, are managed through CCAMLR. This requires a range of sustained environmental, biological, and ecosystem-level observations. CCAMLR takes an ecosystem approach to management, and this require access to data sets that contribute to understanding the whole ecosystem, the physical environment within which it sits, and the rates of change in both of these systems. Specific areas where accessible, sustained, and integrated decisions can contribute include the management of the marine protected areas, which have been established by CCAMLR. Additionally, the Antarctic Treaty System’s “Committee for Environmental Protection” provides recommendations to manage the impact of other human activities in Antarctica, including climate change, and as such requires sustained observations of environmental conditions. It is expected to benefit from improved observations that enhance our understanding of environmental change, including the implications this will have for logistical and scientific operations.
The network of 53 NAPs has a broad remit to support strategic science, logistics, and their national commitments to Antarctic Treaty obligations. Further, their operations require observationally based services, such as sea ice and weather forecasts that are coordinated through programs such as the International Ice Chart Working Group (IICWG), and the World Meteorological Organization (WMO). Industry-based activities such as fisheries and tourism (coordinated through International Association of Antarctic Tourism Operators, IAATO) also require observationally based environmental information, and can additionally enhance opportunistic ship-based collection of data, as a strong statement of commitment to Treaty obligations toward environmental protection.
The influence of SOOS on policy is through the mechanisms described above for the Antarctic Treaty System, and also in terms of inputs to the Intergovernmental Panel for Climate Change (IPCC) assessment process. SOOS-supported datasets informed the last major assessment (AR5 in 2013) and are underpinning much of the Southern Ocean material in the ongoing Special Report on Oceans and Cryosphere in a Changing Climate (scheduled for release in 2019). Such data are also used to test and challenge climate projection models used by the IPCC and are critical to assessments of oceanic influence on the Antarctic Ice Sheet and hence global sea-level rise. The IPCC process includes direct connection with policy makers and outlining of response options, enabling the use and recognition of SOOS-supported observations.
Fundamentally for SOOS, the primary end-users are the scientists and research communities that collect and bring together the diverse observations to answer societies evolving questions on how the Southern Ocean is changing, and what the ramifications are for humanity. The Southern Ocean scientific community, through the NAPs, SCAR, SCOR, the World Climate Research Program (WCRP), and the IMBeR project, provides the scientific knowledge and recommendations that underpin the management and policy decisions.
Delivering the breadth of observations required by these end-users is an enormous task, and is greater than can be provided within each forum or by any one nation alone – a key driver for the development of SOOS in 2011. Over the last 7 years, SOOS has worked with all stakeholders to build networks and connections around the identified data priorities. With these structures now in place, the next decade sees a strong lean toward designing a network of regional systems that incorporate all overlapping end-user requirements where possible. This will not only facilitate the delivery of data to end-users, but also enable funders to quantify and broaden their impact and up-take. Working with end-users and organizations such as the Committee of Managers of National Antarctic Programs (COMNAP), the SOOS Regional Working Groups will be central to developing and implementing these observing systems in an integrated and flexible way.
Significant investment in data collection over the last decade has enhanced knowledge of Southern Ocean systems and their impact on the Earth system. Yet, the Southern Ocean remains poorly observed leading to uncertainty in estimates of future states of Southern Ocean processes and the consequences for the Earth system.
This community paper assesses decades of research and observational efforts in the Southern Ocean to provide forward-looking priorities that require sustained observations over the coming decade. Distilled into eight key issues, these are identified as the major data bottlenecks in addressing the SOOS Science Themes that have underpinned the focus of SOOS networks and efforts thus far. For Themes 1 and 2, the role of the Southern Ocean in the planet’s heat and freshwater balance, and the stability of the Southern Ocean overturning circulation, respectively, observations of bottom water production processes are critical, and should be prioritized in the coming decade (Key Issue 1). Key Issue 2 on “reducing uncertainties in air-sea and air-sea-ice fluxes of heat, momentum, freshwater, and carbon” is a cross-cutting issue that delivers into each of the six Science Themes, and is fundamental in modeling efforts to project future states of Southern Ocean systems. Theme 3 on “The role of the ocean in the stability of the Antarctic Ice Sheet” is imperative to better constrain uncertainties in the contribution of the Antarctic Ice Sheet to future sea level. Key issue 3 supports this by prioritizing efforts to observe the contribution of oceanic heat to ice-shelf basal melt. The “future and consequences of Southern Ocean carbon uptake” is Theme 4, and fundamental to this are observations that enable constraining of the seasonal carbon cycle (Key issue 4). Theme 5 on “The future of Antarctic sea ice” is a broad challenge underpinned by two Key Issues “Integrating sea-ice satellite and
Further, the above disciplinary priorities share common needs for observation systems priorities:
Enhanced observations of most variables from non-summer seasons are needed. Year-round use of autonomous vehicles year-round where possible, deployment of sustained moorings, and other time-series platforms, as well as focused autumn/winter observational programs are needed to address this critical data gap.
A strong relationship between implementation of new technologies and development of internationally agreed standards for collection, quality control, and management of the new data, delivered where possible in alignment with the FAIR data principals is a critical need. This requires appropriate funding, and will ensure that new data streams are high-quality, openly available, integrated data sets – following the example of Argo and other successful ocean observing programs.
Related to this, standardization and aggregation of similar observations are vital. This requires concerted, long-term data management efforts to discover, quality control, standardize, and publish aggregated datasets for both historic and future observations.
Requirements for the full suite of observations needed by the broad end-user community must be quantified and underpinned by robust observing system design efforts. The end-user community includes numerical modelers and scientists from other disciplines. The requirements need to be delivered across disciplinary barriers, through existing or new forums. In this way, the combined community can advocate for sustained efforts that deliver across user needs.
Further, models should be better incorporated into the observing system design and evaluation. As the data-stream grows, these models can be used to semi-automate data quality control. Moreover, data assimilation can be exploited to extract maximum value from the observations and provide gridded products for baseline assessments of the Southern Ocean state.
Remote-sensing data are vital for achieving observational coverage across large spatio-temporal scales for all disciplines. The Southern Ocean community must identify mechanisms to better articulate and advocate their requirements to Space Agencies.
Emerging direct human pressures will also require monitoring in the coming decade. Global issues such as organic pollutants, ocean plastics, and over-fishing are gaining attention. Although mechanisms exist for the reporting of pollutant and waste spills, plastics and fishing catch south of 60°S (e.g., through COMNAP, CEP, and CCAMLR), the impacts on the Antarctic ecosystems are not yet routinely observed and monitored. Some efforts are being made for single-species monitoring [e.g., Southern Ocean Persistent Organic Pollutants Program (SOPOPP)
In the past decade, SOOS and the Southern Ocean community have made considerable progress toward designing a comprehensive and sustainable observing system by integrating existing efforts. In the next decade, the focus will turn to addressing the gaps in the system through a combination of technical innovation and greater coordination and sharing of data and logistics.
LN and EH: section “Abstract.” AC, MMM, and LN: sections “Impetus and Progress Toward Developing a Southern Ocean Observing System” and “The Vision.” LN: sections “A Decade of Progress,” “Drivers of the Future Development of SOOS,” and “Southern Ocean Observations: Future Priorities.” AM and JS: section “Themes 1 and 2: The Role of the Southern Ocean in the Planet’s Heat and Freshwater Balance; and the Stability of the Southern Ocean Overturning Circulation.” AW and RC: section “Theme 3: The Role of the Ocean in the Stability of the Antarctic Ice Sheet and Its Future Contribution to Sea-Level Rise.” SH and KH: section “Theme 4: The Future and Consequences of Southern Ocean Carbon Uptake.” PH, TM, RM, and BO: section “Theme 5: The Future of Antarctic Sea Ice.” DC and IS: section “Theme 6: Impacts of Global Change on Southern Ocean Ecosystems.” KK and AM: section “Observing Antarctic Bottom Water Production Processes.” SS and SG: section “Reducing Uncertainties in Air-Sea and Air-Sea-Ice Fluxes of Heat, Momentum, Freshwater, and Carbon.” KA and EvW: “Understanding the Contribution of Oceanic Heat to Ice-Shelf Basal Melt.” TM, RM, and PH: “Toward a Better Understanding of Processes Controlling Antarctic Sea-Ice Variability and Change.” IJS, RM, and PH: section “Observing Sea-Ice Thickness and Volume.” SM, SF, and ES: “Constraining the Seasonal Carbon Cycle.” RT: sections “Constraining Biological Energy Pathways,” “Assessing Status and Trends of Key Southern Ocean Taxa,” and “Southern Ocean Modelling Progress and Priorities.” RF: sections “Southern Ocean Modeling: Progress and Priorities,” “Required Ocean Modeling Efforts,” and “Ecosystem Modeling Efforts.” MM and LN: “Essential Ocean Variables and Observing System Design.” GW, OS, LN, PB, JB, RM, and SD: section “Priorities for Future Observational Technologies.” AC, SS, EH, MW, and LN: section “International Coordination and End-User Engagement.” LN, MW, EH, and PB: section “Conclusion and Recommendations.”
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.
This paper is a joint contribution of the SCAR–SCOR Southern Ocean Observing System, and the CLIVAR–CliC–SCAR Southern Ocean Regional Panel (SORP), in addition to many authors from the broader Southern Ocean community. The authors thank Stacey McCormack for development of
More information on SOOS Capability Working Groups at
A worldwide system of deepwater reference stations,
A global array of free-drifting profiling floats,
SOCCOM Project:
SOCLIM field studies with innovative tools:
Coordinated through the SCAR program “Antarctic Sea Ice Processes and Climate,”
Twenty-four GEOTRACES cruises and process studies occurring between 2006 and 2018 across all sectors of the Southern Ocean (Atlantic: 8; Indian: 12; Pacific: 7) (
Figure showing links between SOOS and GOOS eEOVs,