Thermal State of Permafrost in Alaska
During the Fourth Quarter of the Twentieth Century

T. E. Osterkamp
Geophysical Institute, University of Alaska, Fairbanks, Alaska, U.S.A.

Abstract

Permafrost temperatures in Alaska increased during the fourth quarter of the twentieth century at sites north of the Brooks Range from the Chukchi Sea to Canada, south along a transect from Prudhoe Bay to Gulkana, and at other sites. Tentative results are presented concerning the characteristics of the warming. Meteorological records, permafrost temperature measurements, thermokarst studies, and modeling efforts suggest the warming occurred statewide. Its magnitude along the transect was 3 to 4°C for the Arctic Coastal Plain, 1 to 2°C for the Brooks Range, and 0.3 to 1°C south of the Yukon River. The warming was seasonal, primarily in winter. Active layer thicknesses on the Arctic Coastal Plain did not increase. Thawing at the permafrost surface and base is occurring and new thermokarst terrain has developed. Probable causes of the warming and thawing include changes in air temperatures, snow cover effects, and combinations of these.

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