source or sink?

UAF prof Chien-Lu Ping has published new findings about the potential for arctic tundra to spew huge amounts of carbon dioxide and methane. Basically, Ping went around the state with a jackhammer (and willing helpers!) and dug test pits in the frozen ground -- more than 100 in all, according to a news release from the university. He found there was a layer of organic matter just above the permafrost and in the top of the permafrost that scientists hadn't accounted for and that could release large amounts of greenhouse gases under continued warming.
According to the release, Ping predicts that a 2-3 degree rise in temperature (unclear whether that's C or F) could switch the tundra from a carbon sink to a carbon source. I need to research that more, because there's been talk for a decade about the arctic tundra becoming a carbon source, although I do remember something about flaws in those old findings...
Photo courtesy of UAF.