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Erosion caused by thawing permafrost around the Arctic Ocean leads to more carbon in the sea, reducing the capability of the water to take up CO2 from the atmosphere. Image credit: Levi Westerfeld / GRID-Arendal

Coastal erosion reduces CO2 uptake in the Arctic Ocean

The oceans have relieved the atmosphere from ¼ of anthropogenic CO2 emissions. In the Arctic, thawing permafrost may weaken this mechanism, new research indicates.

Ocean water absorbs CO2 from the air. So far about a quarter of all the CO2 from anthropogenic emissions has been removed from the atmosphere this way. In the water, CO2 dissolves into carbon species. 

This uptake is particularly efficient in cold waters like those of the Arctic Ocean. What would happen if this water contained more carbon in the first place? 

A recently published study indicates that coastal erosion may reduce the Arctic Ocean’s ability to absorb CO2 from the air. 

As coastal permafrost thaws and waves crash against weakened cliffs, soil and organic material are flushed into the sea. These substances contain carbon, releasing CO2 as they degrade microbially. This brings the water closer to saturation, leaving less room for CO2 from the atmosphere. 

Simulations run with Earth system models indicate that the CO2 uptake by the Arctic Ocean, from the atmosphere, may be reduced by 7–14 percent by the year 2100, compared to simulations run without considering coastal permafrost erosion. 

Jöran März, from the Geophysical Institute at the University of Bergen, and the Bjerknes Centre for Climate Research, is one of the researchers behind the new study, led by the German Max Planck Institute for Meteorology. 

On a global scale, he explains, the effect of thawing, coastal permafrost is weak compared to other positive climate feedbacks that are in the order of a hundred times larger. However, comparing it to the technologies so far developed to mitigate climate change, shows why the question deserves attention. 

“Putting it into perspective, at the end of the century thawing coastal permafrost contributes tens to hundreds of times more to atmospheric CO2 increase than the currently developed CO2 removal technologies presently take up,” Jöran März says. 

“This demonstrates the need to increase efforts to reduce CO2 emissions.”

References

Nielsen, D.M., Chegini, F., Maerz, J. et al. Reduced Arctic Ocean CO2 uptake due to coastal permafrost erosion. Nat. Clim. Chang. 14, 968–975 (2024). https://doi.org/10.1038/s41558-024-02074-3 

Nielsen, D.M., Chegini, F., Maerz, J. et al. Addendum: Reduced Arctic Ocean CO2 uptake due to coastal permafrost erosion. Nat. Clim. Chang. 14, 1003 (2024). https://doi.org/10.1038/s41558-024-02133-9