Fragments From Floyd

Not good. Melting permafrost in Alaska and Siberia turns out to have even more of a downside than had been originally appreciated. It turns out, according to a recent study, that it represents a carbon source (not frozen but in its rapidly thawing state) that is almost equal to that of all land vegetation in its contribution to atmospheric carbon dioxide. Melting permafrost, then, is yet another of those "positive feedback" components in which global warming is creating conditions that amplify the rate of global warming.

Preliminary assessments by scientists from Russia, the University of Florida, and the University of Alaska Fairbanks indicate that loess permafrost, which covers more than a million square kilometers in Siberia and Alaska, is a large carbon reservoir with the potential to be a significant contributor of atmospheric carbon, yet it is seldom incorporated into analyses of changes in global carbon reservoirs.

"The unique aspect of the Siberian loess permafrost is that it is quite deep--20 to 40 meters--and has a surprisingly high carbon concentration at depth for a mineral soil," said Terry Chapin, co-author from the Institute of Arctic Biology at UAF. "This paper explains the processes that led to the accumulation of large amounts of soil carbon and the processes that could lead to its return to the atmosphere."

The largest carbon reservoir on Earth is the ocean, which scientists estimate holds about 40,000 gigatons; soils contain about 2,500 Gt and vegetation about 650 Gt. According to the authors, about 500 Gt of carbon are contained in the thaw-threatened loess, also called yedoma, of Siberia and Alaska.

"If these rates continue as field observations suggest, most carbon in recently thawed yedoma will be released within a century--a striking contrast to the preservation of carbon for tens of thousands of years when frozen in permafrost," state the authors.