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Arctic Tundra Leaking Greenhouse Gases

A profound change appears to be sweeping the landscape above the Arctic Circle: Northern Alaska's tundra is warming up, perhaps because of local climate change. And as it warms, it is releasing more carbon dioxide into the atmosphere than it's soaking up, according to a report at the annual meeting of the American Geophysical Union in San Francisco this week. The findings suggest that a sustained global warming because of human activity could unleash a flood of carbon dioxide from the arctic tundra, which could alter the region's environment and nudge up global temperatures.

Each summer, University of Michigan biologist George Kling and several dozen colleagues from other institutions spend several weeks tracing the whereabouts of carbon dioxide, methane, and other gases in the environment around the National Science Foundation's Toolik Lake research station on Alaska's North Slope. Previous field seasons have shown that the tundra--which in the summertime is a patchwork of soggy tussocks and meltwater lakes--is saturated like a wet sponge with carbon dioxide and methane. "What we didn't know is just how much carbon is entering the atmosphere through contact with surface waters," Kling says.

In the latest field season, Kling's gas-flux team gathered data and fed it into a computer model describing how carbon is stored and released in the permafrost marshes in the Kuparuk watershed, an 8100-square-kilometer area that includes Toolik Lake. They found that about 2.5 grams of carbon per square meter is now entering the atmosphere as carbon dioxide and methane. Previous studies had shown that for thousands of years the arctic tundra was a carbon sink.

Scientists are concerned that this trickle of greenhouse gases may represent the first cracks in a dam, as the arctic tundra stores an estimated 180 billion metric tons of carbon--about a third of the total in the Earth's atmosphere, says Kling. "The concern is what will happen in the future as global warming increases and melting permafrost exposes more of this buried carbon to be respired and released into the atmosphere," he says. As it does, this cold place could turn up the heat on the rest of the planet.