NSF-funded Research: Largest Recorded Tundra Fire Yields Scientific Surprises

The Anaktuvuk River fire from the air

Photo credit: Alaska Fire Service
The 2007 Anaktuvuk River fire.

7/28/2011

In 2007, the largest recorded tundra fire in the Arctic released approximately as much carbon into the atmosphere as the tundra has stored in the previous 50 years.

A study of the Anaktuvuk River fire on Alaska’s North Slope revealed how rapidly a single tundra fire can offset or reverse a half-century worth of soil-stored carbon. The study’s results are published in the July 28 issue of the journal Nature.

Tundra soils store huge amounts of carbon hundreds to thousands of years old. Layers of organic soil insulate the permanently frozen ground, called permafrost, below and restrict fires to aboveground plants and plant litter leaving the carbon stored in soils relatively intact.

As arctic summers get warmer and dryer, so too do the soils, which are highly flammable and able to burn more deeply when dry. This allows fires to burn more deeply into the ground. When aboveground plant materials burn, that not only releases carbon into the atmosphere, it also speeds thawing of the permafrost below. The once-frozen organic material in the thawing permafrost then begins to decompose, releasing additional carbon and amplifying climate warming.

 “Fire has been largely absent from tundra for the past 11,000 or so years, but the frequency of tundra fires is increasing, probably as a response to climate warming,” said co-author Syndonia “Donie” Bret-Harte, an ecosystem ecologist at the University of Alaska Fairbanks Institute of Arctic Biology. “If the frequency of these fires remains at long intervals, 80 to 150 years, then the tundra has time to recover. If these fires occur more frequently, say every 10 years or so, then the landscape cannot recover.”

The Anaktuvuk River fire burned 401 square miles, an area roughly the size of Cape Cod and visible from space, and released more than 2.3 million tons of carbon into the atmosphere. Radiocarbon dating of the soils revealed the maximum age of the soil carbon emitted from the fire was 50 years.

Read the rest of the Institute for Arctic Biology story here.