Scientists: Surface permafrost may vanish in Alaska

Posted: Sunday, November 08, 2009

FAIRBANKS - Alaska probably will see most of its surface permafrost vanish by the end of this century, but researchers believe vast areas of frozen soil will remain deeper underground even as air temperatures increase.

The future of Alaska's permafrost is being closely watched by scientists because of the implications it may have on the climate as a whole. Vladimir Romanovsky, a professor at the University of Alaska Fairbanks Geophysical Institute, discussed evolving permafrost research this week during a teleconference through the Alaska Center of Climate Assessment and Policy.

Using models that predict a 4- to 6-degree rise in Alaska air temperatures by 2100, Romanovsky projects slowly vanishing areas of permafrost in the state. Dozens of bore holes are being monitored throughout Alaska to see how permafrost reacts to changing temperatures.

The research has both short-term and long-term significance. Unstable thawing permafrost can cause enormous damage to buildings and other infrastructure, and it releases gases that are widely believed to contribute to global warming.

"It could be a significant player in the carbon cycle in the atmosphere," Romanovsky said.

Virtually all of Alaska is a potential permafrost region, with only Southeast, the Aleutians and Kodiak Island spared from common permafrost patches. The North Slope and Brooks Range are almost entirely blanketed with permafrost, and most of interior Alaska is constantly frozen.

That's expected to change in the next century. Romanovsky and his team of UAF researchers predict a warming trend that will gradually thaw most of the state's surface permafrost. By the end of the century, only the North Slope will remain frozen.

"It doesn't mean permafrost is disappearing," Romanovsky said, because the frozen soil is deeper and more vast than it appears.

Beyond a depth of about 30 feet, he said, the permafrost is generally expected to remain stable, regardless of the temperatures above.

Most of Interior Alaska is classified as a discontinuous permafrost region, where 50 to 90 percent of the land is constantly frozen. The patches around Fairbanks range from 31.6 degrees to 28 degrees Fahrenheit and reach a depth of as much as 200 feet.

Near Prudhoe Bay, permafrost has been found at depths of 2,000 feet, Romanovsky said.

The surface warming is important, however, because most vegetation is located in the top 10 feet of permafrost. As it thaws, it releases a pair of greenhouse gases - methane and carbon dioxide.

With data going back as far as 50 years or more, researchers have seen mixed thawing patterns since the state emerged from a cold snap in the 1960s and 1970s.

Alaska saw a dramatic increase in permafrost thawing in the 1990s, but the trend has slowed in the past decade, particularly in inland areas.

In the Interior, the picture is muddled. Many permafrost sites have been largely unchanged this decade. A few permafrost areas have even seen cooling trends in the past three years.

Romanovsky said the explanation is probably a thin early winter snow cover in recent years. Without a thick layer of insulating snow, soil has a chance to freeze even harder in tussock-laden terrain.

"Some years the snow isn't deep enough to cover these tussocks," Romanovsky said. "You see a cooling effect."

Because of factors such as snow cover, predicting the rate of permafrost thawing can be imprecise. Romanovsky's projections also don't take into account the creation of new lakes and wetlands as surface permafrost thaws. Romanovsky said they could potentially cause more thawing at deeper levels.

"That could actually accelerate the destruction of permafrost," he said.

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