Abrupt Thaw of Permafrost Beneath Arctic Lakes could Fuel Climate Change

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 Arctic landscape stores one of the largest natural reservoirs of organic carbon in the world in its frozen soils. 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. Permafrost is already thawing in some parts such as lakes beneath the Arctic.

"We have no 200 or 300 years waiting for vast carbon emissions from the eternal ice, says the study's lead author Katey Walter Anthony, an ecologist from the University of Alaska in Fairbanks". 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. Within my lifetime, my children's lifetime, it should be ramping up. She goes on to point out that the releases aren't happening at a fast rate at the moment, "but within a few decades, they should peak".

With an worldwide team of researchers from United States and Germany, Walter Anthony used field measurements and computer models, reaching the grim conclusion: compared to previous estimations, the thawing doubles the greenhouse emissions that come from permafrost.

The study concluded that even if humans reduce the global carbon emissions, methane releases from the abrupt thawing will still take place. "When the lakes form, they flash-thaw these permafrost areas", said Walter Anthony, who is an associate professor at the UAF's Water and Environmental Research Center. Thermokarst lakes form when substantial amounts of ice in the deep soil melts to liquid water.

What specifically worries scientists is that once frozen soil melts, the bacteria that lived in it and hibernated inside of it melts as well, and exits their hibernation.

"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.

This abrupt thawing of the permafrost beneath the lakes is especially unsafe because unlike shallow and gradual thawing of terrestrial permafrost, it is impossible to reverse it this century. "And we have very easily measured ancient greenhouse gases coming out". "Over a few decades, thermokarst lake growth releases substantially more carbon than lake loss can lock in permafrost again [when the lake bottoms refreeze]". However, Walter Anthony believes including them in future models is important for understanding the role of permafrost in the global carbon budget.

This type of lake-related thawing has not been incorporated into previous climate change models, Walter Anthony noted.