Alaska's eroding permafrost signals urgent global warming threat

Professor Nathan D. Brown, author of the publication in "AGU Advances" magazine, explains: "In the Northern Hemisphere, much of the ground is permafrost, meaning it is frozen year-round. Permafrost is a delicate natural resource. If it is lost faster than it is regenerated, we endanger infrastructure and release carbon, which can warm the atmosphere."

Rivers play a key role in maintaining the balance of this resource. In Alaska, the land along riverbanks often consists of permafrost—a mix of soil, gravel, and sand, often bonded with ice.

A team of Texas researchers, in collaboration with experts from other universities, conducted detailed studies to better understand the characteristics of permafrost in this region. They mapped and dated the floodplain deposits, estimated the extent of permafrost, and characterized the vegetation along the Koyukuk River in Alaska, a tributary of the Yukon River stretching over 800 kilometres.

Based on the collected data, they created a model of the changes occurring in the permafrost with changing air temperatures. Although new permafrost forms along the river's floodplain, it does not form fast enough to replace what is disappearing due to rising temperatures.

The main question in warming climate conditions is: will Arctic rivers cause the erosion of permafrost on thawing banks faster than permafrost can renew? "By dating these permafrost deposits, we found that permafrost formation in this region can take thousands of years," explains Dr Brown.

The scientist warns that under warming climate conditions, the process of forming permafrost will likely take longer. Thawing riverbanks made of permafrost will become more susceptible to erosion. The ultimate result will be the loss of permafrost and the release of carbon into the atmosphere.