Arctic seabed traps most carbon from thawing permafrost, limiting greenhouse gas release

A team from the Alfred Wegener Institute and MARUM examined sediment cores taken near Herschel Island, Canada, to trace the fate of carbon released as Arctic permafrost thaws. Their measurements indicate that up to 0.02 gigatonnes of land-derived organic carbon enter the ocean annually, a flux expected to rise sharply by 2100. Chemical and isotopic signatures show that marine microbes break down only about ten percent of this material, releasing it as CO₂, while the remaining ninety percent is sequestered in the seafloor.

The microbes appear to favor newer algal carbon over the older permafrost carbon, reducing the amount that re-enters the atmosphere. Researchers caution that some permafrost carbon may already be partially degraded before deposition, and they plan further investigations during the 2027 Arctic Pulse campaign. The findings provide a clearer baseline for climate models assessing the long-term effects of permafrost thaw on global warming.