HR: 10:20h
AN: C42A-01 INVITED     [Abstracts]
TI: Columbia Glacier, Alaska, at Mid-Retreat
AU: * Pfeffer, W T
EM: pfeffer@tintin.colorado.edu
AF: Institute of Arctic and Alpine Research, University of Colorado, 1560 30th St, Boulder, CO 80303 United States
AB: Columbia Glacier, which terminates in a grounded calving margin in Prince William Sound in central coastal Alaska, has retreated 15 km in the last 25 years, and with annually-averaged speeds in excess of 25 meters per day, it is among the world's fastest glaciers. Discharge flux of ice to the ocean has now exceeded 7 cubic kilometers of ice per year, making it also the largest single glacial contributor to sea level in North America and a prime example of the potent influence of non-linear glacier response to climate forcing. It is a model for similar dynamic responses which may already be occurring in Greenland and Antarctica. Columbia Glacier has been carefully observed, principally by aerial photogrammetry, since the onset of its retreat in the early 1980s. This record is now being supplemented by terrestrial photogrammetry, optical surveying, seismic observations, and oceanographic observations. These observations document the evolving geometry, velocity and strain rate during the retreat and give insights into the iceberg calving process, changing force balance during retreat, and the processes responsible for the apparent irreversibility of tidewater retreat. The retreat is now at its midpoint, with another 15 km of retreat expected before the terminus reaches shallow water. As the glacier terminus passes the principal constriction in its channel and the deepest water yet encountered (in excess of 500 m), Columbia Glacier may now undergo further changes unlike those observed up to this time. This talk provides an overview of observations of Columbia Glacier made up to this time, a summary of present understanding of tidewater retreat, a discussion of the similarities and differences between tidewater retreat and ice sheet outlet glacier dynamics, and informed speculation on the near future for Columbia Glacier.
UR: http://tintin.colorado.edu
DE: 0720 Glaciers
DE: 0730 Ice streams
DE: 0732 Icebergs
DE: 1600 GLOBAL CHANGE
DE: 1641 Sea level change (1222, 1225, 4556)
SC: Cryosphere [C]
MN: Fall Meeting 2005