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Study looks at thawing permafrost

Posted: October 29, 2012 - 10:13pm  |  Updated: October 29, 2012 - 10:15pm

ANCHORAGE — A new study led by the U.S. Geological Survey refines estimates of how frozen Arctic soils could thaw and release gases into the atmosphere, including nitrogen, which could have an effect on plants and water.

Lead author Jennifer Harden, a USGS research soil scientist, said it’s too soon to make grand statements about nitrogen’s effect.

“It’s sort of a flag to look at it and measure it in different environments,” she said from Menlo Park, Calif. “As of yet, it looks like a very small amount of N2O goes to the atmosphere in the north, and probably the bigger concern about nitrogen is its impact on the water resources and on the changes in the vegetation in response to that nitrogen.”

Gardeners know nitrogen as a critical nutrient and the first ingredient listed on commercial fertilizer, she said.

The study looked at three kinds of permafrost, or permanently frozen ground, and how they will thaw as climate warms. The frozen soils vary by their organic matter. A subgroup known as histels, she said, is “very peaty.”

“It would be like freezing sphagnum moss that you buy at the nursery,” she said. After they thaw, they are vulnerable to burning by wildfires unless submerged.

Carbon can be released by burning or through microbes.

“Either way, the carbon’s going to come out when you thaw it,” she said.

Two other soil types have higher mineral content.

“What this paper was trying to say is that, ‘Look, not all of these soils are alike, and when they thaw, their vulnerabilities to different kinds of climate forcings will be different,” she said.

The information should assist climate modelers, she said.

The study’s authors plugged soil numbers into a model that will be used in the next Intergovernmental Panel on Climate Change. The exercise confirmed previous estimates for carbon release in the next century — 850 billion tons, which would double the amount stored in the atmosphere now.

The study concludes that up to 44 billion tons of nitrogen could be released.

“We were able to say, ‘Is this a small number we can ignore or is that a big enough number that we need to do a lot more science on it?’” she said. “The latter is clear. We need to do a lot more science on it.”

USGS Director Marcia McNutt said in the study announcement that the research quantifies the impact on Earth’s two most important chemical cycles, carbon and nitrogen, from thawing of permafrost.

“While the permafrost of the polar latitudes may seem distant and disconnected from the daily activities of most of us, its potential to alter the planet’s habitability when destabilized is very real,” she said.

The study was published in in the journal Geophysical Research Letters.

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