Vol. 20, No. 15
May 3, 2001
Permafrost thawing study focuses on potential effects
Scientists from UD and Russia are working together to identify areas in which the thawing of permafrost in the Northern Hemisphere's circumpolar region could imperil manmade structures, including energy production facilities and transportation links.
The study, the first broad-scale picture of the potential hazards of permafrost thaw brought about by global climate changes, is reported in the April 19 issue of Nature magazine.
Frederick E. Nelson and Nikolay I. Shiklomanov, Department of Geography and Center for Climatic Research, have teamed with Oleg A. Anisimov of the State Hydrological Institute in St. Petersburg, Russia, to conduct the research.
With respect to permafrost, two key changes have occurred in the circumpolar region in recent decades, Nelson said. Those are an increase in human activity and warming, thawing and disappearance of permafrost because of global warming.
Permafrost, which is defined as any earth material at or below 0 degrees Celsius continuously for two or more years, lies beneath and is insulated by the surface layer of materials. The "active layer" is a layer of seasonally thawed ground between permafrost and the surface. A substantial increase in the thickness of the active layer has potentially serious consequences for structures because it can result in dramatic changes in the land surface wherever the permafrost is rich in ice.
If ice-rich permafrost thaws and water drains from the site, subsidence may occur, possibly inflicting damage to any structures on the surface, Nelson explained, citing reports that have been received from Siberia. "With global warming, such a process could be widespread, affecting both ecosystems and the human infrastructure," he said.
The research team is looking at different climate change scenarios that could affect thaw-induced subsidence to better identify specific areas of concern. To do that, the researchers are using a digital map of permafrost and ground ice developed by the International Permafrost Association, a consortium of scientists from the U.S., Canada, Russia and Scandinavia.
"The significance of the paper is that it points out broadly defined areas where we might be concerned about the long-term potential for thawing permafrost," Nelson said. "We are working to document the contraction of the area underlain by permafrost and looking at those places that could stand further study."
The Nature paper notes that "much of the existing infrastructure built in northern regions is located in areas of high hazard potential." That includes northwest Siberia, which contains Russia's Nadym-Pur-Taz natural gas production center, and far eastern Russia, which includes several population centers and the Bilibino nuclear power station. In northwestern North America, specifically Alaska, transportation facilities and pipelines are built through areas identified as being at high risk.
Permafrost thaw and subsidence can be dealt with through the proper engineering of construction projects. "An important aspect of permafrost thaw is that it is not necessarily a rapid process," Nelson said. "It can be accounted for through sound planning."
Because changes evolve gradually, they can be predicted and monitored to allow for a "mitigation of negative consequences and avoidance of catastrophic events," the paper states.
Nelson grew up in Michigan and became interested in Alaska and the circumpolar regions based on stories told by his father, who served in the Alaskan bush during World War II.
He spent several summers on Alaskan glaciers and loved it, leading to his interest in the region's geography. Nelson has been working with Anisimov since 1988, when a thaw of a different naturethat in global politicsled him to propose a research project in conjunction with the Russian scientific community.
Shiklomanov is a UD research assistant who works with Nelson and Anisimov. He plans to remain at UD as a postdoctoral scholar after finishing his doctoral program next month.