HR: 17:45h
AN: C24A-08    [Abstracts]
TI: Geomorphologic Changes in an Active Sub-Arctic Thermokarst
AU: * Kodial, P
EM: ftpsk@uaf.edu
AF: Department of Civil and Environmental Engineering, University of Alaska Fairbanks PO Box 755900, Fairbanks, AK 99775-5900 United States
AU: Toniolo, H
EM: ffhat@uaf.edu
AF: Department of Civil and Environmental Engineering, University of Alaska Fairbanks PO Box 755900, Fairbanks, AK 99775-5900 United States
AU: Toniolo, H
EM: ffhat@uaf.edu
AF: Water and Enviromental Research Center, University of Alaska Fairbanks, Fairbanks, AK 99775-5860 United States
AU: Hinzman, L
EM: ffldh@uaf.edu
AF: Water and Enviromental Research Center, University of Alaska Fairbanks, Fairbanks, AK 99775-5860 United States
AU: Yoshikawa, K
EM: ffky@uaf.edu
AF: Water and Enviromental Research Center, University of Alaska Fairbanks, Fairbanks, AK 99775-5860 United States
AB: In an ongoing study of the rapidly evolving thermokarst located in the Caribou-Poker Creeks Research Watershed - Alaska, a number of geomorphologic changes were observed during the 2004 and 2005 field studies. Evidence of a talik formation at the active layer-permafrost boundary, achieved by a GPR survey conducted in March 2005, is indicative of a lowered permafrost table. Comparison of active layer depths between 1999 and 2005 further corroborate the deepening of the active layer. Bank failure is attributed to the piping mechanism. Interflow by piping was the driving force for the high sediment transport rate. Sediment concentrations profiles at selected study sites designated as `upstream' and `downstream' are of a higher order compared to the 2004 summer. Thermo-erosional niche formation by fluvio-thermal erosion process triggered block failures and subsequent cryogenic transport. Transition from clear to muddy sediment flow was a month earlier this summer and drastic. Thalweg profiles obtained from topographical surveys clearly indicate sediment infilling of the pre-existent depression at the downstream site as well as the newly formed channel-like feature at the upstream site. A smooth channel bed profile can be discerned. In undisturbed shallow test sites the soil temperature profiles were consistently uniform. But in the disturbed sites the temperature gradient was pronounced (8 ° C variation in 1 m).The accelerated growth of the thermokarst has made the contiguous areas more susceptible to further geomorphologic changes.
DE: 0702 Permafrost (0475)
DE: 0706 Active layer
DE: 0708 Thermokarst
SC: Cryosphere [C]
MN: Fall Meeting 2005