HR: 17:15h
AN: C34A-06    [Abstracts]
TI: Sub-glacial Water Pressures Over Long Time Scales and Extended Spatial Scales
AU: * Humphrey, N F
EM: neil@uwyo.edu
AF: Dept. of Geology and Geophysics, Univ. of Wyoming, Dept. 3006, 1000 University Ave, Laramie, WY 82071 United States
AU: Fudge, T
AF: Dept. of Geology and Geophysics, Univ. of Wyoming, Dept. 3006, 1000 University Ave, Laramie, WY 82071 United States
AU: Harper, J T
AF: Dept. of Geology, Univ. of Montana, 32 Campus Dr. \#1296, Missoula, MT 59812 United States
AU: Pfeffer, W T
AF: INSTAAR, Univ. of Colorado, Campus Box 450, Boulder, CO 80309 United States
AB: Data on the sub-glacial hydrologic conditions under the Bench Glacier, coastal Alaska, have been obtained over the full length of the glacier and have been recorded continuously spanning 3 summer melt seasons and 2 winters. Data includes basal water system measurements of ionic conductivity, turbidity, water speed, and water pressure. This talk focuses on approximately 2.5 years of pressure data from up to 43 boreholes, spanning the full length of the glacier and taken at time intervals ranging from 15min intervals down to months of 1 second data. This unique data set reveals the spatial and temporal variability of the sub-glacial hydraulic system. Despite gross similarities between years, there are major differences in the yearly behavior. In particular, both the long term average and short term detailed pressure behavior varies from year to year, both in individual boreholes and in regions of the glacier. Strong differences are noted between the ablation region, which shows a complex record, and the accumulation zone, with a subdued pressure history. The difference appears to be stepwise in space and not a gradual change. Although there is correlation between individual glacial movement or speed events and basal water pressure events, there is no evidence of persistent correlations between ice sliding velocity and basal water system pressures averaged over any spatial or temporal scale. We also report on several anomalous events seen in the record, in particular, we report on sort lived, very high pressure spikes that are rare but apparently not unique aspects of the basal hydrologic system.
DE: 1827 Glaciology (1863)
DE: 1863 Snow and ice (1827)
SC: Cryosphere [C]
MN: 2004 AGU Fall Meeting