In northern Alaska, Dr. Romanovsky said, permafrost is warming rapidly but is still quite cold. In the central part of the state, much of it is hovering just below the freezing point and may be no more than a decade or two from widespread thawing.
The permafrost carbon thus represents a dangerous amplifying feedback or vicious cycle whereby warming leads to accelerated emissions, which leads to further warming.
That's especially true since sea ice loss in the Arctic is happening faster than every major climate model projected — and accelerated Arctic warming and permafrost loss was linked to ice loss in a 2008 study by leading tundra experts.
We find that simulated western Arctic land warming trends during rapid sea ice loss are 3.5 times greater than secular 21st century climate-change trends.
A troubling trend has emerged recently: Wildfires are increasing across much of the north, and early research suggests that extensive burning could lead to a more rapid thaw of permafrost.
One day in 2007, on the plain in northern Alaska, a lightning strike set the tundra on fire.
Historically, tundra, a landscape of lichens, mosses and delicate plants, was too damp to burn. But the climate in the area is warming and drying, and fires in both the tundra and forest regions of Alaska are increasing.
The Anaktuvuk River fire burned about 400 square miles of tundra, and work on lake sediments showed that no fire of that scale had occurred in the region in at least 5,000 years.
Scientists have calculated that the fire and its aftermath sent a huge pulse of carbon into the air — as much as would be emitted in two years by a city the size of Miami. Scientists say the fire thawed the upper layer of permafrost and set off what they fear will be permanent shifts in the landscape.
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