Abstracts
SEARCH Open Science Meeting
October 27, 2003
Seattle, Washington, USA
Degradation of Ice Wedges in Northern Alaska in Response to Recent Warmer Temperatures
Torre Jorgenson1, Erik Pullman2, Yuri Shur 3
1ABR, Inc., PO Box 80410, Fairbanks, AK, 99708, USA, Phone 907-455-6777, Fax 907-455-6781, tjorgenson@abrinc.com
2ABR, Inc., PO Box 80410, Fairbanks, AK, 99708, USA, Phone 907-455-6777, Fax 907-455-6781, epullman@abrinc.com
3Department of Civil and Environmental Engineering, University of Alaska Fairbanks, PO Box 755900, Fairbanks, AK, 99775, USA, Phone 907-474-7067, Fax 907-474-6087, ffys@uaf.edu
Ground observations and photogrammetric analysis indicate that there has been extensive degradation of the surfaces of ice wedges over a 57-year period on the Beaufort Coastal Plain in northern Alaska. Field observations and sampling at 46 polygonal troughs and their intersections showed that ice wedge degradation has been relatively recent as indicated by newly drowned vegetation. We found thermokarst was widespread on a variety of terrain conditions, but most prevalent on ice-rich centers of old drained lake basins and alluvial-marine terraces, which have the greatest ice wedge development in the studied landscape. Ice wedges on these terrains typically occupy from 10 to 20 % of the upper permafrost. We attributed the natural degradation to warm weather during the last decades, because disturbance of the ground surface, which could have similar impact on ice wedges, was not evident.
While ice-wedge degradation probably has been periodically occurring at low rates over the preceding centuries, it has greatly accelerated during the last several decades. Spectral classification of 1945 and 2001 aerial photography found flooding covered 13.7% of the terrestrial area (larger waterbodies excluded) in 1945 only, 3.8% in 2001 only, and 2.2% in both years. We attributed the increase in newly flooded areas (3.8% of landscape) in 2001 (a dry year) not present in 1945 (wet year) to be the result of thermokarst. The waterbody coverage provides only a minimum estimate of ice-wedge degradation, however, because ground observations indicated that many polygonal troughs over ice-wedges had indications of subsidence, yet were not sufficiently low to be covered by water. Qualitative analysis of photography from 1980 indicated that widespread ice wedge degradation had not yet occurred. The ice-wedge degradation indicates that substantial thermokarst can occur in response to decadal-scale temperature changes even in areas of cold continuous permafrost. Changes likely will increase during the next century, if arctic air temperatures increase by 3°–8° C as expected.
Abstract Categories: Changes on Land
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