Most of Arctic's Near-Surface Permafrost May Thaw by 2100December 20, 2005
The study, using the NCAR-based Community Climate System Model (CCSM), is the first to examine the state of permafrost in a global model that includes interactions among the atmosphere, ocean, land, and sea ice as well as a soil model that depicts freezing and thawing. Results appear online in the December 17 issue of Geophysical Research Letters.
"People have used models to study permafrost before, but not within a fully interactive climate system model," says NCAR's David Lawrence, the lead author. The coauthor is Andrew Slater of the University of Colorado's National Snow and Ice Data Center.
About a quarter of the Northern Hemisphere's land contains permafrost, defined as soil that remains below 32 degrees F (0 degrees C) for at least two years. Permafrost is typically characterized by an active surface layer, extending anywhere from a few centimeters to several meters deep, which thaws during the summer and refreezes during the winter. The deeper permafrost layer remains frozen. The active layer responds to changes in climate, expanding downward as surface air temperatures rise. Deeper permafrost has not thawed since the last ice age, over 10,000 years ago, and will be largely unaffected by global warming in the coming century, says Lawrence.
Recent warming has degraded large sections of permafrost across central Alaska, with pockets of soil collapsing as the ice within it melts. The results include buckled highways, destabilized houses, and "drunken forests"-trees that lean at wild angles. In Siberia, some industrial facilities have reported significant damage. Further loss of permafrost could threaten migration patterns of animals such as reindeer and caribou.
The CCSM simulations are based on high and low projections of greenhouse-gas emissions for the 21st century, as constructed by the Intergovernmental Panel on Climate Change. In both cases, the CCSM determined which land areas would retain permafrost at each of 10 soil depths extending down to 11.2 feet (3.43 meters).
For the high-emission scenario, the area with permafrost in any of these layers shrinks from 4 million to just over 1 million square miles by the year 2050 and decreases further to about 400,000 square miles (1 million square kilometers) by 2100. In the low-emission scenario, which assumes major advances in conservation and alternative energy, the permafrost area shrinks to about 1.5 million square miles by 2100.
"Thawing permafrost could send considerable amounts of water to the oceans," says Slater, who notes that runoff to the Arctic has increased about 7 percent since the 1930s. In the high-emission simulation, runoff grows by another 28 percent by the year 2100. That increase includes contributions from enhanced rainfall and snowfall as well as the water from ice melting within soil.
The new study highlights concern about emissions of greenhouse gases from thawing soils. Permafrost may hold 30% or more of all the carbon stored in soils worldwide. As the permafrost thaws, it could lead to large-scale emissions of methane or carbon dioxide beyond those produced by fossil fuels.
"There's a lot of carbon stored in the soil," says Lawrence. "If the permafrost does thaw, as our model predicts, it could have a major influence on climate." To address this and other questions, Lawrence and colleagues are now working to develop a more advanced model with interactive carbon.
This study was funded by the National Science Foundation, which is NCAR'S primary sponsor, and the U.S. Department of Energy.
The National Snow and Ice Data Center (NSIDC) is part of the Cooperative Institute for Research in Environmental Sciences at the University of Colorado. Visit the NSIDC Web site.
National Center for Atmospheric Research
Related Permafrost Current Events and Permafrost News Articles
Permafrost soil: Possible source of abrupt rise in greenhouse gases at end of last Ice Age
Scientists from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) have identified a possible source of carbon dioxide (CO2) and other greenhouse gases that were abruptly released to the atmosphere in large quantities around 14,600 years ago.
Extreme weather in the Arctic problematic for people, wildlife
The residents of Longyearbyen, the largest town on the Norwegian arctic island archipelago of Svalbard, remember it as the week that the weather gods caused trouble.
If trees could talk
Permafrost thaw drives forest loss in Canada, while drought has killed trees in Panama, southern India and Borneo.
Certain Arctic lakes store more greenhouse gases than they release
New research, supported by the National Science Foundation (NSF), counters a widely-held scientific view that thawing permafrost uniformly accelerates atmospheric warming, indicating instead that certain Arctic lakes store more greenhouse gases than they emit into the atmosphere.
Huge waves measured for first time in Arctic Ocean
As the climate warms and sea ice retreats, the North is changing. An ice-covered expanse now has a season of increasingly open water that is predicted to extend across the whole Arctic Ocean before the middle of this century.
Wetlands Likely to Blame for Greenhouse Gas Increases: Study
A surprising recent rise in atmospheric methane likely stems from wetland emissions, suggesting that much more of the potent greenhouse gas will be pumped into the atmosphere as northern wetlands continue to thaw and tropical ones to warm, according to a new international study led by a University of Guelph researcher.
Researchers Find 3-million-year-old Landscape Beneath Greenland Ice Sheet
Glaciers and ice sheets are commonly thought to work like a belt sander. As they move over the land they scrape off everything - vegetation, soil and even the top layer of bedrock.
Methane climate change risk suggested by proof of redox cycling of humic substances
The recent Yokahama IPCC meeting painted a stark warning on the possible effects of gases such as methane - which has a greenhouse effect 32 times that of carbon dioxide.
Researchers: Permafrost thawing could accelerate global warming
A team of researchers lead by Florida State University have found new evidence that permafrost thawing is releasing large quantities of greenhouse gases into the atmosphere via plants, which could accelerate warming trends.
Permafrost Thaw Exacerbates Climate Change
The climate is warming in the arctic at twice the rate of the rest of the globe creating a longer growing season and increased plant growth, which captures atmospheric carbon, and thawing permafrost, which releases carbon into the atmosphere.
More Permafrost Current Events and Permafrost News Articles