Polar oceans (Arctic and Antarctic) store and transport carbon via “polar blue carbon”, but current science and policy frameworks are not yet ready to fully recognize or count it in climate strategies.

A new review published in Global Change Biology (around 9 October 2026) by an international team from the Horizon Europe project POMP (Polar Ocean Mitigation Potential), led by researchers at Aarhus University (including lead author Nadescha Zwerschke and coordinator Mikael Sejr), assesses what is known about carbon captured, stored, or transported by polar marine ecosystems.

Key points from the review

• Polar marine ecosystems can lock carbon into sediments and living tissue for decades, centuries, or longer. Habitats of interest include certain coastal and shelf systems; less is known about phytoplankton, ice- associated algae, microphytobenthos, and carbon in fjord, shelf, and deep- sea sediments.⁠
• These systems are changing rapidly due to warming, ice loss, erosion, and rising human pressure. Some may gain importance as carbon stores while others weaken.
• Traditional “blue carbon” frameworks (developed mainly for tropical and temperate coastal wetlands such as mangroves, salt marshes, and seagrasses) do not readily apply. Polar areas are largely absent from national greenhouse- gas inventories, carbon- market methodologies, and related policies, despite the Arctic and Southern Ocean together covering roughly one- fifth of the global ocean and warming especially fast.

Why policy is not ready

Major uncertainties remain around measurement standards, additionality, permanence (threatened by rapid environmental change), and governance (fragmented or contested jurisdictions, especially in Antarctica under the Antarctic Treaty System/CCAMLR and parts of the Arctic). Treating polar blue carbon as a conventional carbon- offset mechanism would therefore be premature.⁠

The authors stress that it is not a substitute for cutting fossil- fuel emissions. Protecting carbon- rich ecosystems can still support broader climate and biodiversity goals.

Recommended actions

The review calls for four coordinated steps:

1. Greater investment in polar blue- carbon research.
2. Precautionary protection of known carbon- rich and vulnerable habitats (polar regions remain among the least protected oceans).
3. Management approaches that consider carbon storage alongside biodiversity.
4. Clearer policy pathways for recognizing substantial natural carbon stores in polar marine ecosystems.⁠

In short, polar oceans contribute to carbon storage, but better science, standardized methods, and adapted policy are needed before they can be reliably “counted”. The priority remains emission reductions, with habitat protection as a complementary measure. The full paper is titled roughly “Status of Polar Blue Carbon: Toward Recognition and Integration in Marine Policy.”

Polar carbon storage (often called polar blue carbon) is quantified by measuring carbon stocks (how much is stored) and sequestration and accumulation rates (how fast it is buried and locked away long- term) in marine ecosystems of the Arctic and Antarctic.

These systems differ from classic tropical and temperate blue carbon (mangroves, salt marshes, seagrasses). Polar storage occurs mainly in sediments (fjords, shelves, deep sea), benthic communities (including on hard substrata), macroalgae and kelp, phytoplankton, ice- associated algae, and related pathways. Measurement is challenging due to remoteness, ice cover, seasonal darkness, and limited standardization.

1. Carbon stocks in sediments (the largest long-term reservoir)

• Collect sediment cores (using gravity cores, multicorers, or box corers; SCUBA or ROVs in shallow areas).
• Determine dry bulk density (mass per volume after drying).
• Measure organic carbon (OC) content, typically via elemental analysis (after acid treatment to remove inorganic carbonates) or loss- on-ignition (LOI) calibrated against elemental analysis.
• Calculate stock as: OC fraction × bulk density × sediment depth and thickness, then scale by area.
• Account for total organic carbon (TOC), sometimes distinguishing autochthonous (local biological) vs. allochthonous sources using biomarkers, C:N ratios, or stable isotopes (δ¹³C, δ¹⁵N).

2. Accumulation and burial rates (sequestration)

• Date cores with radioisotopes, primarily ²¹⁰Pb (half-life ~22 years, for recent decades- centuries) and sometimes ¹⁴C for longer timescales. Correct for porosity, compaction, and the surface mixed layer (bioturbation).
• Multiply the mass accumulation rate by the buried OC concentration (below the mixed layer).
• Optionally correct for the fraction of local (e.g., algal) carbon using biomarkers and for any inorganic carbon effects.⁠

Example results from Arctic fjords show OC burial rates on the order of several to tens of g C m⁻² yr⁻¹, varying strongly by location.

3. Living biomass and standing stocks

• Direct sampling of benthic fauna, macroalgae and kelp, or ice algae (SCUBA, trawls, grabs, or ice cores).
• Measure wet and dry weight and convert to carbon content (typically ~10- 50% of dry mass depending on tissue).
• Indirect methods: underwater imagery and photography (photo- quadrats or video), acoustics, or remote sensing for habitat extent and density.

Shallow Antarctic Peninsula studies have estimated hundreds of tonnes of C km⁻² in rocky vs. soft-substratum communities.

4. Fluxes, primary production, and pathways

• Primary production: incubations, ¹⁴C uptake, oxygen sensors, or satellite- derived chlorophyll and models.
• Export and biological carbon pumps: sediment traps, particle imaging, or models of vertical flux.
• Other metrics (prioritized for standardization in high- latitude work): particulate organic carbon (POC), functional groups (phytoplankton, microbes, benthos, macroalgae), habitat mapping, and export/migration processes. A recent review identified 23 key metrics for polar and sub- polar biological carbon pathways and recommended standardization plus modeling for scaling.

5. Scaling up and remote sensing

• Combine field data with satellite, airborne, or UAV imagery, acoustic surveys, and ecosystem models to estimate extent and total stocks over large, inaccessible areas.
• Machine learning and geospatial models help map hotspots (e.g., certain Arctic shelf seas).

Key challenges and current limitations

• Methods for traditional coastal blue carbon are better standardized (e.g., Blue Carbon Initiative manuals), but polar adaptations are still developing, measurement, additionality, permanence, and governance remain uncertain.
• Ice, logistics, and high spatial variability limit data density.
• Stocks alone do not equal permanent sequestration; burial efficiency, remineralization, and future climate impacts (warming, ice loss, erosion) must be considered.
• Experts emphasize greater investment in research, precautionary habitat protection, and clearer policy pathways before polar blue carbon can be reliably “counted” in climate frameworks.

Status of Polar Blue Carbon: Toward Recognition and Integration in Marine Policy

This is the full open- access perspective paper “Status of Polar Blue Carbon: Toward Recognition and Integration in Marine Policy” by Nadescha Zwerschke and co-authors (including many from Aarhus University and the POMP project), published in Global Change Biology (2026; 32:e71098).

Core message

Polar (Arctic and Antarctic) marine ecosystems store significant carbon and are becoming more important as CO₂ uptake shifts poleward under climate change. However, current science and policy frameworks are not yet ready to fully recognize or “count” polar blue carbon in climate strategies. The authors call for better research, precautionary protection, and clearer policy pathways, while stressing that this is not a substitute for cutting fossil- fuel emissions.

Key habitats reviewed (Table 1)

The paper distinguishes actionable (*) systems (already somewhat recognized, e.g., seagrass and saltmarsh) from emerging (°) systems that are less studied but potentially important:

• Saltmarsh & seagrass (Arctic mainly; limited Antarctic data): Relatively low carbon accumulation rates (CAR) compared with tropical systems, but still relevant; facing coastal infrastructure, pollution, etc.
• Macroalgae and kelp: Large potential area in the Arctic (~340,000 km²); expanding with ice loss; CAR largely unknown.
• Microphytobenthos, phytoplankton, ice-associated algae: Substantial production; export and long-term burial poorly quantified.
• Sediments (fjord, shelf, glacial troughs, deep sea): Often the main long-term store. Fjord sediments can show high CAR (e.g., tens to hundreds of g C m⁻² yr⁻¹ in some Arctic and West Antarctic Peninsula sites). Shelf and deep-sea rates are lower but the areas are vast.

Many extents, growth and or decline trends, and CAR values remain poorly constrained, especially in the Antarctic.

Knowledge gaps (Table 2)

Major gaps include:

• Accurate extent and standing stocks.
• Carbon accumulation rates (CAR) and greenhouse- gas fluxes across most habitats.
• Responses to multiple climate drivers (light, nutrients, warming, ice loss, terrestrial carbon delivery).
• Remineralization rates, carbon sources (marine vs. terrestrial), and long- term sequestration efficiency.
• Effects of human pressures (seafloor disturbance, pollution, resource extraction) as polar regions become more accessible.

Policy and management recommendations

• Polar regions are among the least protected oceans (~4–5% managed/no-take).
• Apply the precautionary principle: protect known carbon-rich and vulnerable habitats now, even before all uncertainties are resolved.
• Adopt holistic, ecosystem- based management that considers carbon storage alongside biodiversity, from source (e.g., kelp or phytoplankton) to sink (sediments).
• Strengthen science- policy links so polar blue carbon can eventually enter NDCs, carbon accounting, and frameworks such as the Kunming- Montreal Global Biodiversity Framework and High Seas Treaty.
• Avoid treating polar blue carbon as conventional carbon- offset credits at present, measurement standards, additionality, permanence, and governance remain inadequate.

Relevance to measuring polar carbon storage

The paper underscores that reliable measurement is still limited. It relies on the same core approaches discussed earlier (sediment cores, bulk density, organic -carbon analysis and radioisotope dating for accumulation rates; biomass sampling; remote sensing and models for scaling) but highlights large data gaps and the need for standardization and more observations, especially under changing climate conditions.

The full PDF is freely available via repositories such as the NERC Open Research Archive (direct link typically ends in /GCB-32-e71098.pdf). Let me know if you’d like a deeper dive into any specific section, table, habitat, or measurement aspect.

Journal: Global Change Biology (2026; 32:e71098)

DOI: 10.1111/gcb.71098

Provided: Aarhus University

Authors: Nadescha Zwerschke, Dorte Krause-Jensen, David K. A. Barnes, Paul E. Renaud, William E. N. Austin, Mathieu Ardyna, Karl Attard, Bodil A. Bluhm, Steeve Comeau, Jean-Pierre Gattuso, Judith Hauck, Eva Leu, Marie Maar, Laurent Oziel, Amanda E. Poste, Vibe Schourup-Kristensen, Camilla Svensen, Jakob Thyrring, Mikael Sejr

First published: 21 September 2026