HR: 15:15h
AN: H23H-06    [Abstracts]
TI: Geophysical imaging of a temperate glacier's hydrologic system in 1, 2, and 3 dimensions
AU: * Bradford, J H
EM: johnb@cgiss.boisestate.edu
AF: Dept. of Geosciences Boise State University, 1910 University Dr., Boise, ID 83725,
AU: Clement, W
EM: billc@cgiss.boisestate.edu
AF: Dept. of Geosciences Boise State University, 1910 University Dr., Boise, ID 83725,
AU: Nichols, J
EM: jnichols@cgiss.boisestate.edu
AF: Dept. of Geosciences Boise State University, 1910 University Dr., Boise, ID 83725,
AU: Brown, J
EM: jbrown@cgiss.boisestate.edu
AF: Dept. of Geosciences Boise State University, 1910 University Dr., Boise, ID 83725,
AU: Mikesell, D
EM: dmikesell@cgiss.boisestate.edu
AF: Dept. of Geosciences Boise State University, 1910 University Dr., Boise, ID 83725,
AU: Harper, J
EM: joel@mso.umt.edu
AF: Dept. of Geosciences University of Montana, 32 Campus Dr., Missoula, MT 59812,
AU: Humphrey, N
EM: neil@uwyo.edu
AF: Dept. of Geology University of Wyoming, 1000 E University Ave, Laramie, WY 82071,
AU: Tschetter, T
EM: tschettj@uwyo.edu
AF: Dept. of Geology University of Wyoming, 1000 E University Ave, Laramie, WY 82071,
AB: Between 1999 and 2007, we conducted a series of geophysical experiments on Bench Glacier in the Chugach Range of southeast Alaska. Objectives of the experiments include measuring 1) the distribution of water in the snow pack, 2) water storage and routing within the glacier, and 3) the geometry of flow paths at the bed of the glacier. To accomplish these objectives, we have deployed georadar at frequencies ranging from 5 MHz to 1 GHz in 1D, 2D, and 3D single and multi-offset configurations. We have conducted time lapse georadar monitoring of the glacier at the annual, seasonal, daily, and minute time scales. We have employed state of the art data processing and analysis tools such as reflection tomography to produce accurate radar velocity profiles, and 3D coherence cube imaging to identify the 3D distribution of voids and fractures within the glacier. We have conducted passive seismic monitoring, 3D seismic reflection imaging, and shear wave seismic reflection surveying designed to both to image hydrologic structures and to provide a direct measure of the glaciers elastic properties. Here we provide an overview of the project and to present notable findings to date. These findings include 1) that there is lateral heterogeneity in the liquid water content of the snow and significant lateral flow within the snow pack, 2) that Bench Glacier is stratified with an upper layer containing few voids and little water, and a lower layer containing significantly greater water content and many voids, and 3) the void spaces in the lower layer appear to be comprised of both fractures and randomly distributed irregular void space. Video borehole measurements coupled with azimuthal anisotropy in the geophysical measurements indicate that the voids are primarily subvertically oriented, have a preferred azimuthal orientation that is oblique to the glacier flow direction, and are present at scales ranging from mm to 10s of m.
DE: 0689 Wave propagation (2487, 3285, 4275, 4455, 6934)
DE: 0776 Glaciology (1621, 1827, 1863)
DE: 0935 Seismic methods (3025, 7294)
DE: 1835 Hydrogeophysics
DE: 1863 Snow and ice (0736, 0738, 0776, 1827)
SC: Hydrology [H]
MN: 2007 Fall Meeting