Permafrost’s future in Alaska looks poor, but the forecast isn’t all bad
ggrosse - Fri, 2009-11-06 16:54
By Jeff Richardson Fairbanks Daily News-Miner
FAIRBANKS — Alaska will probably 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 like 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.
Contact staff writer Jeff Richardson at 459-7518.
