STEVE INSKEEP, Host:
NPR's Christopher Joyce reports on what may be a new trend in the Arctic.
CHRISTOPHER JOYCE: It's peak field season right now for scientists who study the Arctic, like Michelle Mack.
MICHELLE MACK: I'm at Toolik Lake field station, in a trailer that's on a gravel pad that's in the middle of Arctic tundra.
JOYCE: Mack is an ecologist from the University of Florida who prefers the desolate beauty of the North Slope of Alaska and the snowcapped Brooks Mountain Range. She says what the Anaktuvuk fire did - burn through 400 square miles of tundra - amazed her.
MACK: We've never seen anything like it in this area. What's surprising is that forests have huge trees, whereas tundra has six-inch tall, tiny little plants.
JOYCE: Nonetheless, the fire sizzled for three months, then burst into a major conflagration before snowfall put it out. So if there weren't any trees, what was there to burn?
MACK: It's coming from the soil.
JOYCE: Organic matter, dead plants, accumulated over decades. And what set it off was dry weather, and then a lightning strike.
MACK: There's been a marked increase in lightning strike activity on the North Slope, particularly in the last 10 years.
JOYCE: But Mack was really surprised when she calculated how much carbon that fire put up into the atmosphere. It was two million tons. Is that a lot? Well, think of it this way: Every year, the Arctic tundra absorbs more carbon from the atmosphere than it releases. It's a net carbon sink. Because carbon warms the atmosphere, the Arctic is actually cooling the planet by taking up carbon. But Mack says the Anaktuvuk fire reversed that equation.
MACK: One fire, that alone is enough to offset the whole uptake.
JOYCE: Geographer Eric Kasischke of the University of Maryland is also in Alaska this week, studying, among other things, why there have been so many more fires there recently. Between the region's big forests and the carbon-rich tundra soil, he says there's a lot of carbon that's at risk of getting loose.
ERIC KASISCHKE: Besides pumping more carbon into the atmosphere, the Arctic fires also melt the permafrost. That's the permanent layer of frozen soil and water underneath the surface. When that disappears, so does a major source of moisture for the tundra.
KASISCHKE: Christopher Joyce, NPR News.
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INSKEEP: This is NPR News. Transcript provided by NPR, Copyright NPR.