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Arctic river deltas store 5% of world’s frozen carbon

An international team of scientists has, for the first time, quantified the total carbon stored in permafrost at the mouth of rivers flowing into the Arctic Ocean.

According to a study recently published in the journal Nature Communications, about 1% of the world’s permafrost surface area lies in Arctic river deltas, which occupy an area about the size of Indiana. But carbon is highly concentrated in these deltas. They contain about 5% of the carbon stored in permafrost worldwide.

This matters because the river deltas — and the Arctic in general — are vulnerable to climate change. As global temperatures rise, permafrost thaws. When permafrost thaws, the previously frozen plant and animal matter begins to decompose, which releases carbon dioxide and methane into the atmosphere.

"Consequently, the thawing permafrost could potentially intensify climate change,” said study co-author Guido Grosse, head of the Permafrost Research Section at the Alfred Wegener Institute in Germany. “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 water is getting warmer. All these destabilizing factors come together in the already very dynamic Arctic deltas."

Scientists from eight countries contributed to the study, including researchers from the University of �黨��Ƶ Fairbanks. Together, they compiled global data from more than 1,600 soil samples taken from 17 Arctic deltas.

"Up to now, the number of studies on Arctic deltas has been very limited," said Matthias Fuchs, the study’s lead author. Fuchs was a postdoctoral researcher at AWI and is continuing his research at the University of Colorado Boulder. “Compared to the previously published studies, the number of drill cores analyzed has almost tripled."

While the study highlights the immense carbon stocks stored in Arctic river deltas, it’s not yet clear how these landscapes will respond to continued warming. That’s because the region likely contains saline permafrost, which thaws at a lower temperature than freshwater permafrost. potentially accelerating thaw, landscape change and the release of stored carbon.

“Saline permafrost represents one of the biggest unknowns in Arctic climate science,” said Benjamin Jones, a co-author on the study and researcher at UAF’s Institute of Northern Engineering. “Because saline permafrost can thaw below 0°C, these landscapes may respond to warming much faster than we previously expected, which could accelerate the release of stored carbon.”

Jones’ current research aims to better understand this variable.

“Through our NSF-funded Thaw Below Zero project, we’re working to better understand how these hidden thaw processes could reshape Arctic deltas, coastlines, ecosystems and infrastructure in the future,” he said.  
 
ADDITIONAL CONTACT: Ben Jones, 907-230-3260, bmjones3@alaska.edu.