From: R. Greenway, ENN
Published October 15, 2009 06:35 AM

Global Warming Threatens to Upset Arctic Carbon Trapping

The US Geological Survey, in partnership with the Ecological Society of America, University of Alaska Fairbanks published the results of a study on the changing climate and the important role that the Arctic plays in sequestering carbon.

The study shows that the arctic could potentially alter the Earth’s climate by becoming a possible source of global atmospheric carbon dioxide. The arctic now traps or absorbs up to 25 percent of this gas but climate change could alter that amount, according to a study published in the November issue of Ecological Monographs.

In their review paper, David McGuire of the U.S. Geological Survey and the University of Alaska at Fairbanks and his colleagues show that the Arctic has been a carbon sink since the end of the last Ice Age, which has recently accounted for between zero and 25 percent, or up to about 800 million metric tons, of the global carbon sink. On average, says McGuire, the Arctic accounts for 10-15 percent of the Earth’s carbon sink. But the rapid rate of climate change in the Arctic — about twice that of lower latitudes — could eliminate the sink and instead, possibly make the Arctic a source of carbon dioxide.

Carbon generally enters the oceans and land masses of the Arctic from the atmosphere and largely accumulates in permafrost, the frozen layer of soil underneath the land’s surface. Unlike active soils, permafrost does not decompose its carbon; thus, the carbon becomes trapped in the frozen soil. Cold conditions at the surface have also slowed the rate of organic matter decomposition, McGuire says, allowing Arctic carbon accumulation to exceed its release.

But recent warming trends could change this balance. Warmer temperatures can accelerate the rate of surface organic matter decomposition, releasing more carbon dioxide into the atmosphere. Of greater concern, says McGuire, is that the permafrost has begun to thaw, exposing previously frozen soil to decomposition and erosion. These changes could reverse the historical role of the Arctic as a sink for carbon dioxide.

The figure shows the mean extent of permafrost in the Arctic, estimated for (a) the years 1990-2000 and (b) the years 2090-2100. In (c), the estimation of loss of permafrost by 2100 is overlaid on estimates for the year 2000. Credit: A. David McGuire, USGS.

For more information: http://www.usgs.gov/newsroom/article.asp?ID=2326&from=rss

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