68th Canadian Geotechnical Conference and 7th Canadian Permafrost Conference

LONG-TERM OBSERVATIONS OF ACTIVE LAYER THAWING AND FREEZING, BARROW, ALASKA

Session: Characterization of Permafrost State and Variability I / Caractérisation et variabilité du pergélisol I

Jerry Brown, Woods Hole (United States)
Frederick Nelson, Northern Michigan University (United States)
Vladimir Romanovsky, Geophysical Institute, University of Alaska (United States)
Cathy Seybold, USDA Natural Resources Conservation Service (United States)
Robert Hollister, Grand Valley State University (United States)
Craig Tweedie, University of Texas at El Paso (United States)

Beginning in the early 1950s and continuing to the present, Barrow has been a region of numerous active layer and permafrost investigations. The average active layer thickness (ALT) obtained by physical probing at two, permanently gridded sites for the periods (1962 -1970) and (1991-present) was 35 cm, with mean minimum of 22 cm in 1992 and a maximum of 45 in 1968. Additional 1970s ALT data from the nearby U.S. Tundra Biome sites are compared with these long-term data. ALT values based on measured soil temperatures from 1997 to present ranged from 33 to 63 cm with final freezeback dates ranging from October 9 to November 12. Average ALT calculated from modeled soil-permafrost temperatures (1924 to present) was 34 cm with a minimum of 18 cm in both 1945 and 1969 and a maximum of 54 cm in 1998. Modeled ALT values are comparable to those determined by temperature point measurements.