Arctic lakes speed up permafrost thawing

Abrupt Thawing of Permafrost Beneath Arctic Lakes could Fuel Climate Change

Abrupt Thawing of Permafrost Beneath Arctic Lakes could Fuel Climate Change

Researchers studied methane released by thawing permafrost under thermokarst lakes in the Arctic.

Its impact on the climate is an influx of permafrost-derived methane into the atmosphere in the mid-21st century, which is not now accounted for in climate projections. When permafrost or the centuries-old frozen ground thaws and warms, it releases methane and carbon dioxide into the atmosphere. These pools significantly speed up the thawing of the permafrost, which leads to food being available to microbes that consequently produce carbon dioxide and methane.

Additionally, Walter Antony and a group of US and German researchers used field measurements and computer models to determine "that abrupt thawing more than doubles previous estimates of permafrost-derived greenhouse warming".

The results of the study also suggest that now is the time that the emissions from thermokarst lakes are also included into global climate models, since they are now the hotspots of permafrost carbon release. Within my lifetime, my children's lifetime, it should be ramping up. The mechanism of this rapid thawing process indicates that this ancient carbon releases 125 to 190 percent faster than it does from simple, gradual thawing by itself.

As part of the study, researchers observed hundreds of thermokarst lakes in Alaska and Siberia during a 12-year period. Thermokarst lakes form when substantial amounts of ice in the deep soil melts to liquid water.

Because the same amount of ice takes up more volume than water, the land surface slumps and subsides, creating a small depression that then fills with water from rain, snow melt and ground ice melt, according to the study. "For decades, can be formed very deep thermal holes to a depth of from several to tens of meters", - says Walter Anthony. They argue that not including them in global climate models overlooks their feedback effect, which occurs when the release of greenhouse gases from permafrost increases warming. Emitted gases consisting of carbon atoms the age of from two thousand to 43 thousand years, quickly rise to the surface and reach the atmosphere.

Team members with the Alfred Wegener Institute (AWI) for Polar and Marine Research in Germany then used U.S. Geological Survey-NASA Landsat satellite imagery from 1999 to 2014 to determine the speed of lake expansion across a large region of Alaska.

"Thermokarst lakes provide a completely different scenario". "Over a few decades, thermokarst lake growth releases substantially more carbon than lake loss can lock in permafrost again [when the lake bottoms refreeze]".

Emissions from thermokarst lakes aren't now factored into global climate models because their small size makes individual lakes hard to include. "You can't stop the release of carbon from these lakes once they form", Walter Anthony added.

"The models that have incorporated permafrost have only treated the land as if there were no lakes", she said.