03. June 2026

For the first time, AWI researchers have performed a detailed calculation of the amount of carbon stored in permafrost in Arctic river deltas. In a new study in the journal Nature Communications, they point out the risks endangering the storage function of these highly sensitive landscapes due to rapid climate change.

Many rivers flow into the Arctic Ocean north of the Arctic Circle - including the Lena in Siberia and the Mackenzie River in Canada. The deltas of these large and small rivers store large amounts of carbon, which is bound there in frozen soils and sediments. Climate change, however, is destabilising the deltas from the ocean and land side and also from the air. For the first time, an international team led by the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) has now provided figures demonstrating the significance of this long neglected and highly vulnerable permafrost region between land and sea. According to the study, Arctic river deltas store 57.5 gigatonnes of carbon on only one per cent of the global permafrost surface. This equals around 5 per cent of the permafrost soil carbon stored in that region. A better understanding of this region, which is so vitally important for the Arctic carbon cycle, is therefore urgently needed.

The permafrost region covers around a quarter of the land area in the northern hemisphere and stores vast amounts of organic carbon in the form of dead plant remains. While this Arctic freezer remained largely stable for many millennia, rising global temperatures are causing the permafrost to thaw. Soil microorganisms then become active over large areas, decompose the organic material and release more carbon into the atmosphere in the form of CO₂ and methane.

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"There is one area, however, that has been somewhat neglected so far: namely the deltas of the many small and large Arctic rivers. It is precisely in these river mouths where traditionally a great deal of carbon supplied by the rivers draining the northern permafrost region is being deposited in soils and sediments that become permafrost over the long term – however, it is this border area between ocean and land that is now under massive pressure from several sides. The sea ice is retreating, the sea level is rising, the land is sinking, while the permafrost is thawing, the thawing season is lengthening, and the river waters and soils are getting warmer. All these factors come together in the already very dynamic Arctic deltas and destabilise a balance that was maintained for millennia."

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