Old Arctic carbon heads to the sea, but the ocean floor retains it

On August 3, 2026, researchers from the Alfred Wegener Institute and MARUM disclosed results about the fate of carbon leaving permafrost and entering the Arctic Ocean. The study, published in Nature Geoscience, shows that most of this carbon remains stored in the seabed.

Permafrost carbon reaches the ocean

The frozen soil of the Arctic contains about 1,300 gigatonnes of organic carbon, predominantly from plant remains. As temperatures rise, permafrost thaws and coastlines fragment, allowing up to 0.02 gigatonne of carbon to be transported annually to the sea via rivers and coastal erosion.

Marine microorganisms prefer fresh carbon

By analyzing sediment cores collected off Herschel Island, scientists observed that bottom-sea microorganisms are selective. They give preference to carbon freshly produced by marine algae rather than the older carbon released from permafrost, as indicated by the ^13C and ^14C isotopes present in pore water.

How much carbon turns into gas

The results reveal that only about ten percent of the organic carbon deposited in the sediments is converted into gases by microorganisms. This gas can rise through the water and eventually reach the atmosphere, contributing to the greenhouse effect, but representing a small fraction of the total transported.

Implications for coastal chemistry and life

The input of sediments and dissolved carbon can reduce the amount of light penetrating coastal waters, making them more turbid. This reduction in light affects algal production, which forms the base of the food chain supporting fish, crustaceans and seals, impacting local ecosystems.

Future investigations in the Arctic Pulse campaign

The authors plan to deepen the research during the international "Arctic Pulse" campaign in 2027, using the Polarstern icebreaker, AWI research aircraft, and terrestrial stations. The goal is to observe how rapid environmental changes remodel Arctic ecosystems and improve the basis for climate models that assess the consequences of permafrost melt.

With information from ScienceDaily.