University of Michigan ecologist George Kling at a landslide thermokarst on a glacial headwall near Toolik Lake, Alaska. As permafrost ice melts, the soil collapses and either creates an erosional hole in the tundra or a landslide such as this one. These features are called thermokarst failures. Photo courtesy of George Kling. Enlarge

Ancient carbon trapped in Arctic permafrost is extremely sensitive to sunlight and, if exposed to the surface when long-frozen soils melt and collapse, can release climate-warming carbon dioxide gas into the atmosphere much faster than previously thought.

University of Michigan ecologist and aquatic biogeochemist George Kling and his colleagues studied places in Arctic Alaska where permafrost is melting and is causing the overlying land surface to collapse, forming erosional holes and landslides and exposing long-buried soils to sunlight.

They found that sunlight increases bacterial conversion of exposed soil carbon into carbon dioxide gas by at least 40 percent compared to carbon that remains in the dark. The team, led by Rose Cory of the University of North Carolina, reported its findings in an article to be published online Feb. 11 in the Proceedings of the National Academy of Sciences.

"Until now, we didn't really know how reactive this ancient permafrost carbon would be—whether it would be converted into heat-trapping gases quickly or not," said Kling, a professor in the U-M Department of Ecology and Evolutionary Biology. EEB graduate student Jason Dobkowski is a co-author of the paper.

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