HR: 14:10h
AN: G33C-03 INVITED    [Abstracts]
TI: GPS and Conventional Surveying Measurement of Glacier and Iceberg Motion in the Jakobshavns Isbrae System
AU: * Fahnestock, M
EM: mark.fahnestock@unh.edu
AF: CSRC/EOS, Uiversity of New Hampshire, 236A Morse Hall University of New Hampshire, Durham, NH 03824, United States
AU: Truffer, M
EM: truffer@gi.alaska.edu
AF: Geophysical Institute, University of Alaska, 903 Koyukuk Dr, Fairbanks, AK 99775-7320, United States
AU: Lüthi, M
EM: luethi@vaw.baug.ethz.ch
AF: VAW/ETH Zurich, Gloriastrasse 37/39, Zurich, CH-8092, Switzerland
AU: Motyka, R
EM: jfrjm@uas.alaska.edu
AF: Geophysical Institute, University of Alaska, 903 Koyukuk Dr, Fairbanks, AK 99775-7320, United States
AU: Amundson, J
EM: amundson@gi.alaska.edu
AF: Geophysical Institute, University of Alaska, 903 Koyukuk Dr, Fairbanks, AK 99775-7320, United States
AU: Brown, J
EM: jed@59a2.org
AF: VAW/ETH Zurich, Gloriastrasse 37/39, Zurich, CH-8092, Switzerland
AB: The lower reach of Jakobshavns Isbrae, a large outlet glacier of the Greenland ice sheet, has changed dramatically in the last ten years. Work to characterize the present patterns and time variation of ice flow in this system has involved several satellite and surface based measurement techniques. Our field efforts over the past two summers have attempted to document time variations in ice flow in the main channel of the glacier, and to characterize motion of the glacier and icebergs in the fjord during large calving events. We have used conventional geodetic GPS systems on the ice where deployment and recovery are reasonable, radio and iridium linked GPS in more difficult areas, and a set of conventional survey reflectors tracked by automatic total station near the terminus to recover a record of ice flow. The glacier experiences large-scale calving retreat events through the summer; our measurements are able to characterize the changes in glacier flow near the terminus across several of these events. In addition, flow in the main branch of the glacier upstream has been followed through two melt seasons; here flow variations appear to be in sync with surface water inputs in the basin. The time series of motion from different parts of the glacier show responses to different forcings; near the terminus the ice flow does not show the strong tidal fluctuations in speed that were observed twenty years earlier by Echelmeyer; while at higher elevations subtle diurnal variations in flow are observed later in the melt season
DE: 0720 Glaciers
DE: 0726 Ice sheets
DE: 0732 Icebergs
DE: 1223 Ocean/Earth/atmosphere/hydrosphere/cryosphere interactions (0762, 1218, 3319, 4550)
DE: 1294 Instruments and techniques
SC: Geodesy [G]
MN: 2007 Fall Meeting