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Study: Tundra fires to blame for thawing permafrost

Permafrost helps store excess carbon, and when it thaws, both carbon and methane are released at accelerated rates.

By Brooks Hays
Study: Tundra fires to blame for thawing permafrost
An aerial view of the 2007 Anaktuvuk River fire in Alaska. Photo by Christopher Arp

FAIRBANKS, Alaska, Nov. 10 (UPI) -- Researchers at the University of Alaska, Fairbanks say tundra fires are to blame for widespread permafrost thawing across the arctic.

To document how fire influences tundra permafrost thawing, a team of scientists from the university and the United States Geological Survey used Lidar to scan areas of Alaskan tundra affected by the 2007 Anaktuvuk River fire. Lidar is a laser-powered remote sensing technology commonly used to build high-resolution maps.

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Researchers used the technology to build a topographical profile of several hundred square miles of tundra. They did so by flying atop the arctic in a Lidar-equipped helicopters -- first two years after the fire and then again three years later. The Lidar results showed a third of the burned acreage to be experiencing permafrost thaw. Thawing was observed in just one percent of the unburned acreage nearby.

"Once you burn off that protective layer, what we observed is the effect isn't immediate but takes a few years to really get going," Chris Arp, assistant professor at the University of Alaska Fairbanks Water and Environmental Research Center, said in a press release.

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Thermokarst featured more prominently among acreage in the fire zone. Thermokarst consist of various irregularities in the tundra topography -- slumping hillsides, hummocks and hollows, all signs of thawing.

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Similar effects of fire on permafrost are more well understood in boreal forests. Tundra fires are much rarer. The latest findings offer a more comprehensive picture of fire and thawing in the arctic.

Arp and his colleagues, who published their findings in the journal Scientific Reports, say understanding the factors that affect permafrost thawing is important because of the tundra's role in the carbon cycle. Permafrost helps store excess carbon, and when it thaws, both carbon and methane are released at higher rates.

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Thawing permafrost can also affect the tundra's diversity of plant life, altering wildlife habitat and water flows downstream.

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