Abrupt Thaw of Permafrost Beneath Arctic Lakes could Fuel Climate Change

Rodiano Bonacci
Agosto 20, 2018

Due to human-caused warming of the atmosphere from greenhouse gas emissions, a gradual thawing of the permafrost is now taking place where the upper layer of seasonally thawed soil is gradually getting thicker and reaching deeper into the ground.

The effort, conducted by a team of USA and German researchers, is part of a 10-year NASA-funded project to better understand climate change effects on the Arctic.

As the Arctic warms, some of its lakes are bubbling.

Permafrost is ground that is frozen year-round. Most of the world's permafrost is found in areas of high latitudes, usually in close proximity to the Antarctic and Arctic regions.

Existing models now attribute about 20 percent of the permafrost carbon feedback this century to methane, with the rest due to carbon dioxide from terrestrial soils. This byproduct then enters into the atmosphere and contributes to climate warming, researchers say. 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. Microbes are waking up and digesting this organic material that has been frozen for centuries. The biggest concern is the rapid rise in methane levels in the atmosphere.

In the latest study, researchers monitored the levels of greenhouse gases released by thawing permafrost beneath thermokarst lakes and their impact on climate change. The study, which was published recently in the journal Nature Communications, talks about the carbon that is released by the thawing permafrost which exists beneath thermokarst lakes.

However, in the presence of thermokarst lakes, permafrost thaws deeper and more quickly.

"Thermokarst lakes provide a completely different scenario".

They found that the abrupt thaw process increases the release of ancient carbon stored in the soil 125 to 190 percent compared to gradual thawing alone.

For the study, Katey Walter, lead author of the study, and her colleagues studied several thermokarst lakes in Alaska and Siberia over a 12-year long period. By including thermokarst lakes, methane becomes the dominant driver, responsible for 70 to 80 percent of permafrost carbon-caused warming this century. "This is already happening, just not very fast, but in a few decades will reach its peak". By combining field work results with remote-sensing data of lake changes during the past two years, they determined the "abrupt thaw" beneath such lakes is likely to release large amounts of permafrost carbon into the atmosphere this century. In a nutshell, whether we are successful at curbing global carbon emissions or continue business as usual, it won't make a difference.

Using a combination of computer models and field measurements, Walter Anthony and an worldwide team of USA and German researchers found that abrupt thawing more than doubles previous estimates of permafrost-derived greenhouse warming.

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