Debris-bed friction of hard-bedded glaciers
Journal of Geophysical Research F: Earth Surface
By: D. Cohen, N.R. Iverson, T.S. Hooyer, U.H. Fischer, M. Jackson, and P.L. Moore
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Abstract
[1] Field measurements of debris-bed friction on a smooth rock tablet at the bed of Engabreen, a hard-bedded, temperate glacier in northern Norway, indicated that basal ice containing 10% debris by volume exerted local shear traction of up to 500 kPa. The corresponding bulk friction coefficient between the dirty basal ice and the tablet was between 0.05 and 0.08. A model of friction in which nonrotating spherical rock particles are held in frictional contact with the bed by bed-normal ice flow can account for these measurements if the power law exponent for ice flowing past large clasts is 1. A small exponent (n < 2) is likely because stresses in ice are small and flow is transient. Numerical calculations of the bed-normal drag force on a sphere in contact with a flat bed using n = 1 show that this force can reach values several hundred times that on a sphere isolated from the bed, thus drastically increasing frictional resistance. Various estimates of basal friction are obtained from this model. For example, the shear traction at the bed of a glacier sliding at 20 m a-1 with a geothermally induced melt rate of 0.006 m a-1 and an effective pressure of 300 kPa can exceed 100 kPa. Debris-bed friction can therefore be a major component of sliding resistance, contradicting the common assumption that debris-bed friction is negligible. Copyright 2005 by the American Geophysical Union.
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | Debris-bed friction of hard-bedded glaciers |
| Series title | Journal of Geophysical Research F: Earth Surface |
| DOI | 10.1029/2004JF000228 |
| Volume | 110 |
| Issue | 2 |
| Year Published | 2005 |
| Language | English |
| Larger Work Type | Article |
| Larger Work Subtype | Journal Article |
| Larger Work Title | Journal of Geophysical Research F: Earth Surface |
| Google Analytic Metrics | Metrics page |