25 December 2005Anchorage Daily NewsDoug O'Harra
Warming temperatures could melt the top 11 feet of permafrost in Alaska by the end of the century -- damaging roads and buildings with sinkholes, transforming forest and tundra into swamps, and releasing vast amounts of greenhouse gases into the air.
This meltdown forecast comes amid other signals that Arctic climate has been changing fast: shrinking sea ice cover, warmer temperatures and shifting vegetation.
A new federal study released last week applied one of the most sophisticated supercomputer climate models ever developed to the future of permafrost. The results were startling.
Under the most extreme scenario, global warming could thaw the top 11 feet of permafrost near the ground surface in most areas of the Northern Hemisphere by 2100, altering ecosystems across Alaska, Canada and Russia on a scale unseen for thousands of years.
And then it gets worse.
Methane and carbon dioxide gas could ooze from the soggy dirt and peat, triggering even faster warming.
"If that much near-surface permafrost thaws, it could release considerable amounts of greenhouse gases into the atmosphere, and that could amplify global warming," said lead author David Lawrence, with the National Center for Atmospheric Research. "We could be underestimating the rate of global temperature increase.
"I think this is another piece of evidence that says we should be considering actions" to reduce emissions of greenhouse gases, Lawrence said.
But a leading permafrost researcher at the University of Alaska Fairbanks disagrees that the thaw could be so large. Alaska's permafrost won't melt that deep or that fast, said Vladimir Romanovsky, who monitors the world's most extensive network of permafrost observatories for the Geophysical Institute.
If air temperatures increase 2 to 4 degrees over the next century, permafrost will definitely begin thawing south of the Brooks Range and start degrading in some places on Alaska's Arctic slope, he said. But a prediction that melting will reach 10 to 11 feet deep over the entire region goes too far, he said.
The computer climate model didn't take into account some natural factors that tend to keep the permafrost cold, Romanovsky said. Deeper permafrost, largely untouched by recent warming at the surface, will have an influence, for instance.
Lawrence said he hopes to collaborate with Romanovsky to fine-tune future work-ups to deal with those deeper layers.
"We'd be excited to work with Vladimir or other scientists like him to improve our modeling," he said.
Permafrost -- earth that remains frozen year-round -- underlies much of Alaska, Canada and Siberia. Intermittent through Interior forests and southern Alaska, permafrost can be more than 1,000 feet deep on the Arctic slope.
Even with his reservations about predictions of widespread permafrost meltdown, Romanovsky agrees that conditions have begun to shift. He's been monitoring the collapses of permafrost caused by human disturbances near his home outside Fairbanks.
During the past few years, permafrost has been flirting with some of the warmest conditions since the ice age ended 10,000 years ago. The record warmth of summer 2004, followed by insulating snows, kept some soil from refreezing all the way down to permafrost over the winter, Romanovsky said.
"That was the first time we saw that on many sites," he said. "It was very unusual."
Then, last summer, with continued warm temperatures, the active layer of thawing earth extended 6 inches deeper into the ground than normal, Romanovsky said.
Such ground melting is only one clue that Arctic climate change may be speeding up. In September, the polar ice cap shrank to its smallest extent in 25 years of satellite monitoring. Tundra has been greening up, with shrubs moving north. Spruce forests are ailing, dry and burned by extensive forest fires. NASA recently reported that 2005 may beat 1998 as the Earth's warmest year on record.
The new permafrost simulations came from some of the most detailed climate models ever made, Lawrence said. Using supercomputers in the United States and Japan, it calculated how frozen soil would interact with air temperatures, snow, sea ice changes and other processes over time. He and his co-author, Andrew Slater from the National Snow and Ice Data Center, analyzed multiple runs of the simulation, viewing virtual permafrost processes over thousands of years.
The study was published Dec. 17 in the journal Geophysical Research Letters and presented earlier in the month at a science conference in San Francisco.
Creating 100 years in cyberspace took about three months of computer time in the real world, Lawrence said.
"This is the state-of-the-art global climate model," he said.
The simulations used the high and the low estimates of how much greenhouse gas will be released into the atmosphere by human activity over the next 100 years, as projected by the Intergovernmental Panel on Climate Change.
Under the worst-case emission scenario, land area with permafrost reaching within about 11 feet of the surface shrinks from about 4 million square miles to 1 million square miles by 2050. By 2100, the near-surface permafrost is practically gone.
Even with the least catastrophic low-emission scenario, the area with permafrost near the surface shrinks by more than 60 percent, to about 1.5 million square miles in 2100. By comparison, all of Alaska covers about 586,000 square miles.
This vast increase in mushy, water-saturated soil will release huge amounts of carbon dioxide and methane into the air and increase the run-off of water into the Arctic Ocean by 28 percent, the scientists said.
Daily News reporter Doug O'Harra can be reached at do'[email protected].
