Papers on Geomagnetism and Paleomagnetism Marine Geology and Geophysics
Mechanical and hydrologic basis for the rapid motion of a large tidewater glacier: 1. Observations
Article first published online: 20 SEP 2012
Copyright 1994 by the American Geophysical Union.
Journal of Geophysical Research: Solid Earth (1978–2012)
Volume 99, Issue B8, pages 15219–15229, 10 August 1994
How to Cite
1994), Mechanical and hydrologic basis for the rapid motion of a large tidewater glacier: 1. Observations, J. Geophys. Res., 99(B8), 15219–15229, doi:10.1029/94JB00237., , , , , , , , , and (
- Issue published online: 20 SEP 2012
- Article first published online: 20 SEP 2012
- Manuscript Accepted: 13 JAN 1994
- Manuscript Received: 16 JUN 1993
Measurements 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−1 to about 7 m d−1. 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 3 days, and occurring 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 in velocity were due, directly or indirectly, to variations in water input to the glacier. The role of basal water in causing the observed glacier motions is interpreted by Kamb et al. (this issue).