Tuesday, July 15, 2008

Fires in Alaska + global warming = more fires?

An interesting article in the Kansas City Star explores data about fires in Alaska and how they might lead to even more fires and possibly affect global warming. In the article, Adrian Rocha, a physiological ecologist is examining a fire that burned last year which was the largest ever recorded on Alaskan tundra--256,000 acres or 400 square miles. Here is an excerpt.

"You can see that the surface is really dark," said Rocha, a researcher at the Marine Biological Laboratory. In fact, the ground is mostly coal-mine black rather than the vibrant green that blanketed the land before fire came.

"More of the sun's energy is heating up the soil," he said.

Just 3 percent of the light that strikes this ash-black ground is reflected back, compared with 18 percent on leafier, unburned ground.

Soil temperatures run 3.6 to 5.4 degrees hotter. And the ground thaw runs about 10 inches deeper than beneath unburned tundra - perhaps because it absorbs more sunlight, maybe because a layer of insulation against winter cold was stripped away, or both.

The fire itself kicked massive amounts of carbon dioxide into the air. All wildfires do that. But even though the Arctic covers less than a sixth of the planet's land mass, it holds about one-third of the planet's stored carbon, in part because of the slow rate of decomposition in the previously frozen north.

With more of that soil taken out of the permafrost, the dirt is awakened to the activity of microbes that could release greater levels of carbon dioxide into the atmosphere.

If the research going on here now finds that happening, the increase in Arctic fires could set in motion what scientists call positive feedback: greenhouse gases making for a hotter, drier Arctic that burns more often and kicks up even more greenhouse gases.

"These fires have everyone thinking this is part of a pattern," said Wendy Loya, an ecologist for the Wilderness Society in Anchorage. "You've got dramatic increases in temperature and a little more precipitation. But the extra rain isn't enough to offset the warmer temperatures and the longer growing seasons. ... You get more fires."

I'm no "physiological ecologist", but it sounds like we're in for a vicious circle. Global warming produces more fires which increases global warming. Here's a little illustration I put together.

1 comment:

John said...

Interesting article. I wonder what else we're going to see in terms of positive feedback?

I read recently that as the oceans warm there is a danger that frozen methane deposits stored beneath them could be released into the atmosphere.

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