Heavier Rains Further Speeding Permafrost; AK Worst-Case - 1" Of Rain Equals 1" Of Melt

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Goldstream Road, outside Fairbanks, Alaska, shows waves where the road has been damaged by permafrost thaw, despite efforts to insulate the underlying permafrost. (Yereth Rosen)

It’s widely understood that rising temperatures in the North are thawing permafrost. And the relationships between permafrost thaw and disturbances such wildfire, landslides and poorly planned construction are also widely understood. Now add another thaw factor: Rain.

A new study that tracked results at a variety of interior Alaska permafrost sites found significant soil thaw in after rainy summers. In the most vulnerable of the sites, there was a one-to-one relationship — a centimeter of rain produced a centimeter of thaw, reported the study, published in the Nature journal Climate and Atmospheric Science.

Arctic precipitation expected to increase as the region warms, and the role of rain in permafrost thaw is just starting to get attention, said lead author Thomas Douglas of the U.S. Army Cold Regions Research and Engineering Laboratory at Fort Wainwright in Alaska. “I think water can be underappreciated in its role, both thermal and hydrological,” Douglas said. Models projecting future thaw tend to focus on other factors, largely warming temperatures, he said. “Precipitation is one that people hadn’t thought of as something to factor in,” he said.

In their study, which used data from 2,750 measurements at permafrost sites, Douglas and his colleagues found that summer rainwater exacerbates current permafrost thawing trends — and does so in two ways. The liquid, which is by definition above freezing, transports heat into the ground, and gravity pulls that heat-carrying water to deeper levels.


Lenses of icy permafrost float along the surface of a small pond in the boreal forest outside Fairbanks, Alaska. Pooling rainwater can be especially potent and hastening permafrost thaw in existing wetlands. (Yereth Rosen)

EDIT

https://www.arctictoday.com/heavy-summer-rains-speed-permafrost-thaw-a-new-study-finds/