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Mechanical and hydrologic basis for the rapid motion of a large tidewater glacier. 1: ObservationsMeasurements of glacier flow velocity and basal water pressure at two sites on Columbia Glacier, Alaska, are combined with meteorological and hydrologic data to provide an observational basis for assessing the role of water storage and basal water pressure in the rapid movement of this large glacier. During the period from July 5 to August 31, 1987, coordinated observations were made of glacier surface motion and of water level in five boreholes drilled to (or in one case near to) the glacier bed at two sites, 5 and 12 km from the terminus. Glacier velocities increased downglacier in this reach from about 4 m/d to about 7 m/d. Three types of time variation in velocity and other variables were revealed: (1) Diurnal fluctuation in water input/output, borehole water level, and ice velocity (fluctuation amplitude 5 to 8%); (2) Speed-up events in glacier motion (15-30% speed-up), lasting about three days, and ocurring at times of enhanced input of water, in some cases from rain and in others from ice ablation enhanced by strong, warm winds; (3) 'Extra-slowdown' events, in which, after a speed-up event, the ice velocity decreased in about 3 days to a level consistently lower than that prior to the speed-up event. All of the time variations were due, directly or indirectly, to variations in water input to the glacier.
Document ID
19950049863
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Meier, Mark
(University of Washington, Seattle, Washington United States)
Lundstrom, Scott
(University of Washington, Seattle, Washington United States)
Stone, Dan
(University of Washington, Seattle, Washington United States)
Kamb, Barclay
(California Institute of Technology, Pasedena, California United States)
Engelhardt, Hermann
(California Institute of Technology, Pasedena, California United States)
Humphrey, Neil
(California Institute of Technology, Pasedena, California United States)
Dunlap, William W.
(University of Washington, Seattle, Washington United States)
Fahnestock, Mark
(NASA Goddard Space Flight Center Greenbelt, Maryland, United States)
Krimmel, Robert M.
(U.S. Geological Survey, Tacoma, Washington United States)
Walters, Roy
(U.S. Geological Survey, Tacoma, Washington United States)
Date Acquired
August 16, 2013
Publication Date
August 10, 1994
Publication Information
Publication: Journal of Geophysical Research
Volume: 99
Issue: B8
ISSN: 0148-0227
Subject Category
Geophysics
Accession Number
95A81462
Funding Number(s)
CONTRACT_GRANT: NSF DPP-86-19348
CONTRACT_GRANT: NSF DPP-86-19352
Distribution Limits
Public
Copyright
Other

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