Published: Sun, August 19, 2018
Research | By Jody Lindsey

Permafrost carbon leak could peak within a few decades

Permafrost carbon leak could peak within a few decades

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.

One key point to keep in mind is that methane is a greenhouse gas that is 22 times stronger than carbon dioxide, and the carbon has already started to leach into the atmosphere as the planet's climate continues to heat up. When researchers combined their fieldwork results with remote-sensing data about changes in the lake during the past two years, they determined the release of greenhouse gases beneath thermokarst lakes is relatively rapid and the thawing of the permafrost beneath such lakes is likely to release large amounts of permafrost gases into the atmosphere this century. 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.

American and German researchers found that abrupt thawing more than doubles previous estimates of permafrost-derived greenhouse warming. 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.

Moreover, the team also found that this abrupt thawing was still a concern even under a scenario in which humans tried to rein in their greenhouse-gas production and slow climate change.

The gradual thaw process was thought to have minimal effect as thawed ground would stimulate the growth of plants, which counterbalance the carbon released into the atmosphere by consuming it during photosynthesis. Such lakes develop when warming soil melts ground ice, causing the surface to collapse and form pools of water.

In the case of these newly-formed lakes, the permafrost will thaw deeper and more rapidly.

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"Within decades you can get very deep thaw-holes, meters to tens of meters of vertical thaw", Walter Anthony said. However, the study's authors show that these lakes are hotspots of permafrost carbon release.

As part of the study, researchers observed hundreds of thermokarst lakes in Alaska and Siberia during a 12-year period. However, a process begins in the event that the permafrost thaws out - soil microbes located in the permafrost convert the carbon into carbon dioxide and methane.

"While lake change has been studied for many regions, the understanding that lake loss and lake gain have a very different outcome for carbon fluxes is new", said co-author Guido Grosse of AWI.

Because the thermokarst lakes are relatively small and scattered throughout the Arctic landscapes, computer models of their behavior are not now incorporated into global climate models. Adding thermokarst methane to the models makes the feedback's effect similar to that of land-use change, which is the second-largest source of manmade warming.

Methane has a significant influence on global warming. The released gases, built with carbon atoms between 2,000 and 43,000 years old, quickly rise up through the lake and into the atmosphere.

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