HR: 0800h
AN: C11A-0079    [Abstracts]
TI: Field Measurement of Past and Present Meltwater Infiltration in the Percolation Zone of the Greenland Ice Sheet
AU: * Harper, J T
EM: Joel@mso.umt.edu
AF: University of Montana, Department of Geosciences 32 Campus Drive #1296, Missoula, MT 59802, United States
AU: Humphrey, N F
EM: neil@uwyo.edu
AF: University of Wyoming, Geology and Geophysics Dept. 3006 1000 University Ave., Laramie, WY 82070, United States
AU: Pfeffer, W T
EM: pfeffer@tintin.colorado.edu
AF: University of Colorado, INSTAAR Campus Box 450, Boulder, CO 80309, United States
AU: Brown, J M
EM: joelmb9877@msn.com
AF: Boise State University, Center for Geophysical Investigation of the Shallow Subsurface MG-206 1910 University Drive, Boise, ID 83725, United States
AU: Schuler, D R
EM: david.schuler@umontana.edu
AF: University of Montana, Department of Geosciences 32 Campus Drive #1296, Missoula, MT 59802, United States
AU: Sturgis, D
EM: dsturgis@uwyo.edu
AF: University of Wyoming, Geology and Geophysics Dept. 3006 1000 University Ave., Laramie, WY 82070, United States
AB: We present results from a field campaign focused on meltwater infiltration and horizontal water transport processes in the percolation zone of the Greenland Ice Sheet. Field data were collected during a period of heavy melt in June/July 2007 along a ~50 km transect (from ~2000 m to ~1600 m elevation) of the EGIG line of west Greenland. Snow and firn stratigraphies of the upper 10 m were documented with snowpit measurements, core analysis of 21 firn cores drilled to 10+ m, and with over 60 km of constant offset radar profiles collected at a variety of frequencies. We also acquired 15 constant midpoint profiles to characterize depth-density relationships in the upper 80 meters of the firn column. Dye tracing experiments were used to identify meltwater migration pathways and to quantify the relative rates of horizontal and vertical water movement. Five thermister strings with 33 channels and a 30 min time base were installed for long term monitoring of the thermal signature of meltwater migration and ice layer formation in the upper 10 m of firn. Two meteorological stations were installed to provide information on surface boundary conditions. Our work shows massive ice layers (up to 0.4 m thick) form at depth under conditions of heavy surface melt. The ice layers, however, lack spatial coherence over meter length scales and therefore allow vertical meltwater infiltration. Hence, we found no evidence of significant horizontal water transport along internal ice layers within this elevation band of the GIS percolation zone.
UR: http://www.umt.edu/geosciences/faculty/harper
DE: 0726 Ice sheets
DE: 0736 Snow (1827, 1863)
DE: 0740 Snowmelt
DE: 0762 Mass balance (1218, 1223)
DE: 0776 Glaciology (1621, 1827, 1863)
SC: Cryosphere [C]
MN: 2007 Fall Meeting