The discovery matters because Arctic permafrost contains an estimated 1,300 gigatonnes of organic carbon, accumulated over thousands of years from plant and other biological remains. A further 400 gigatonnes are stored in marine and river-delta sediments. As the Arctic warms faster than any other region on Earth, thawing ground and rapidly eroding shorelines are transferring increasing quantities of this material into rivers and coastal waters. Researchers estimate that as much as 0.02 gigatonnes of carbon currently enter the sea each year, and climate projections suggest that this flow could increase by 70 to 150 percent by 2100.

Once organic carbon reaches the ocean, its climate effect depends largely on what happens next. Microorganisms can consume the material and convert it into dissolved carbon dioxide and other gases, some of which may eventually reach the atmosphere. Alternatively, the carbon can settle into marine sediments, where it may remain stored for decades, centuries or longer. Until now, scientists have had limited information about the balance between these two pathways, particularly in Arctic coastal environments where erosion, thawing and marine biological activity interact.

To investigate the process, the research team collected sediment cores at different distances from the coast of Herschel Island. These cores preserve layers of material deposited over approximately 50 years, creating a historical record of carbon entering the nearshore environment. The scientists examined the physical and chemical composition of the sediments and determined how quickly permafrost-derived deposits accumulated on the seabed. Their central question was not simply how much carbon arrived, but how much was actually consumed by microorganisms after burial.

The team used pore water—the fluid trapped in microscopic spaces between sediment grains—as a chemical record of microbial activity. When microorganisms digest organic matter, they release dissolved inorganic carbon, including carbon dioxide, into these tiny cavities. By measuring the concentration of this dissolved carbon, researchers could estimate how much organic material had been decomposed. The team also analyzed carbon isotopes, forms of carbon with different atomic masses, to identify the origin and age of the material being consumed.

The carbon-13 isotope helped distinguish between carbon originally produced on land and carbon derived from marine organisms. Carbon-14 provided an additional time signature: ancient permafrost carbon contains far less radiocarbon than recently produced marine organic matter because radioactive carbon decays over time. This allowed the researchers to determine whether sediment-dwelling microorganisms were feeding primarily on old carbon released from permafrost or on fresh carbon generated by algae and other marine life.

The results revealed an unexpected microbial preference. Although large quantities of terrestrial organic carbon are carried away from the eroding coast, microorganisms in the sediments appeared to favor fresher marine carbon, including recently produced algal remains. Only about 10 percent of the organic carbon in the sediments was converted into gases that could rise through the water column and potentially contribute to atmospheric greenhouse gas concentrations. The majority remained buried in the seabed, meaning that permafrost-derived carbon had a smaller immediate role in the active coastal carbon cycle than many scientists had feared.

The finding does not mean that thawing permafrost is harmless or that its carbon can be excluded from climate models. Some of the ancient organic material may be decomposed before it reaches the seabed, either on land, in rivers or within the water column. The study also focused on a specific Arctic coastal setting, and microbial behavior may differ in other regions, particularly where water temperatures, oxygen availability, sediment composition or marine productivity are different. Nevertheless, the research demonstrates that the fate of permafrost carbon is controlled by a complex series of biological and geological filters rather than by a simple direct transfer from frozen ground to atmosphere.

The movement of this material may also reshape Arctic coastal ecosystems even when its greenhouse-gas impact is limited. Eroding sediment can make seawater cloudy, reducing the sunlight available to algae for photosynthesis. Dissolved organic carbon can darken the water further, altering light penetration and potentially changing marine productivity. Because algae form the base of food webs supporting fish, crustaceans, seals and communities that depend on coastal resources, changes in sediment and carbon transport could affect food availability and ecosystem health. Researchers plan to examine these connections during the international Arctic Pulse campaign, scheduled for 2027, using coordinated observations from the research icebreaker Polarstern, aircraft and land-based stations. By showing how much carbon remains safely stored beneath the seafloor—and how little of the decomposed fraction comes from ancient permafrost—the study offers a crucial new benchmark for predicting the climate and ecological consequences of a rapidly changing Arctic.

Subject of Research: Arctic permafrost-derived organic carbon, microbial decomposition, coastal erosion, marine sediments, and carbon storage

Article Title: Limited remineralization of Arctic permafrost-derived organic carbon in nearshore marine sediments

News Publication Date: 31-Jul-2026

Web References: https://www.awi.de/ueber-uns/service/presse/presse-detailansicht/default-d3bd6640772aaf799e98095e01f80024.html; https://www.awi.de/im-fokus/arctic-pulse.html

References: Nature Geoscience; DOI: 10.1038/s41561-026-02060-8

Image Credits: Alfred-Wegener-Institut / Jaroslav Obu

Keywords: Permafrost, Arctic ecosystems, climate change effects, carbon sinks, coastal erosion, organic carbon, Arctic Ocean, marine sediments, greenhouse gases, carbon sequestration

Natural hydrocarbon seepage, including methane emissions, has long been recognized as a crucial component of the Earth’s carbon cycle. However, capturing detailed data on these emissions, especially from inaccessible polar continental margins, has remained a formidable challenge. This new study combines novel fieldwork conducted in the frigid waters off Northeast Greenland with robust datasets collected from prior industry-led expeditions. Such a comprehensive approach has enabled scientists to trace the migration pathways of hydrocarbons from their subterranean sources through the sedimentary layers and ultimately into the ocean, providing an unprecedented look at these natural phenomena.

Methane, a potent greenhouse gas, plays a significant role in climate dynamics. The researchers’ findings offer critical insights about methane’s natural flux within the Arctic, distinguishing long-term natural seepages from emissions potentially intensified by anthropogenic climate change and rising ocean temperatures. This differentiation is essential for refining climate models and predicting future greenhouse gas dynamics. Christoph Böttner emphasizes that understanding these emissions’ baseline conditions is vital to comprehending how ongoing environmental changes may alter the Arctic’s contribution to global carbon cycles.

Northeast Greenland’s continental shelf is emerging as an invaluable natural laboratory for studying these processes. Its remoteness and the complexity of its geological history, shaped over millennia by glaciers, ice movements, tectonic shifts, and erosive forces, have left the area understudied until now. The region’s dynamic transformation under rapidly changing Arctic conditions positions it uniquely to reveal how natural oil and gas seepage responds to shifts in environmental parameters, including sea temperature increases and ice cover retreat.

Adding further weight to the significance of this research, co-author Marit-Solveig Seidenkrantz, Professor at Aarhus University’s Department of Geoscience, highlights the broader ecological and climatic context. Oil and gas seepage does more than influence carbon fluxes; it affects marine ecosystems from microscopic organisms to larger fauna adapted to polar marine environments. These hydrocarbons shape biological processes and food webs in ways that are only now beginning to be understood, underscoring the interconnectedness of geological and biological systems in the Arctic.

Climate change’s impact on the Arctic’s thermal regime is exceptional, with warming rates up to four times the global average. This accelerated warming profoundly influences the stability of methane reservoirs within the continental shelf sediments. The study provides the first direct evidence for gas hydrates—ice-like crystalline substances formed by the trapping of gas molecules within water molecules under high-pressure and low-temperature conditions—in this region. Gas hydrates represent a significant potential source of methane emissions if destabilized by rising temperatures and changing pressure regimes, an outcome that could create positive feedback loops amplifying global warming.

Frank Werner Jakobsen, a PhD researcher focusing on Northeast Greenland sediments at UiT The Arctic University of Norway, clarifies that understanding the gas hydrates’ current state, spatial distribution, and vulnerability to environmental changes is crucial for predicting future methane emissions. Moreover, the research contributes valuable knowledge regarding the geological evolution of the seafloor, elucidating how glacial retreat, sediment transport, and tectonic activity have molded the subaquatic landscape over thousands of years, subsequently influencing hydrocarbon migration pathways.

The team quantified that since the last glacial period ended roughly 15,000 years ago, between 677 and 1,460 million tonnes of hydrocarbon gases—equivalent to 0.5 to 1.1 billion tonnes of carbon—have seeped naturally into the ocean. This extensive, prolonged activity highlights natural seepage’s role as not merely a contemporary process but a long-standing geological phenomenon. Such data are vital for contextualizing modern emissions and evaluating anthropogenic impacts against natural background levels.

Importantly, the research forewarns that future hydrocarbon releases could accelerate in response to ongoing warming of Arctic waters. As sea temperatures rise, destabilization of gas hydrates and enhanced seepage could contribute additional methane to the atmosphere, heightening concerns over feedback mechanisms in climate change scenarios. Christoph Böttner underscores the need for comprehensive baseline data sets to inform these predictions and guide climate models more accurately, emphasizing that many Arctic shelf areas remain uncharted in terms of hydrocarbon seepage status.

Despite the clear evidence and implications, the broader ecological and global climatic consequences of pervasive hydrocarbon seepage in the Arctic remain insufficiently understood. The study’s integrative approach closes a critical gap by elucidating seepage patterns and their interaction with widespread geological and environmental changes, providing a foundation for deeper inquiry into methane’s role in polar carbon budgets and ecosystem dynamics.

Given the rapid transformation of polar regions under the force of climate change, factoring natural methane emissions from Arctic shelves into predictive climate models is imperative. The research team advocates for incorporating their comprehensive findings into future climate projections, improving the accuracy of greenhouse gas budgets and anticipating potential shifts in global climate trajectories. Their work calls attention to the Arctic as a vital, albeit vulnerable, component of Earth’s climate system.

Ultimately, this pioneering study of the Northeast Greenland continental shelf’s hydrocarbon dynamics not only enhances our scientific understanding of Arctic natural methane cycles but also highlights the urgency of continued exploration and monitoring. As global warming advances, insights like these are essential for informing mitigation strategies, environmental policies, and our collective response to the challenges posed by climate change’s accelerating pace in Earth’s polar regions.

Subject of Research: Not applicable

Article Title: Natural hydrocarbon seepage at the Northeast Greenland continental shelf

News Publication Date: 12-Nov-2025

Web References: https://doi.org/10.1038/s43247-025-02932-8

References: Böttner, C., Seidenkrantz, M.-S., Jakobsen, F. W., et al. (2025). Natural hydrocarbon seepage at the Northeast Greenland continental shelf. Nature Communications Earth & Environment. DOI: 10.1038/s43247-025-02932-8

Image Credits: Not provided

Keywords: Arctic Hydrocarbon Seepage, Methane Emissions, Gas Hydrates, Northeast Greenland, Climate Change, Carbon Cycle, Marine Geoscience, Arctic Warming, Seafloor Geology