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Detailed Reference Information |
Cohen, D., Iverson, N.R., Hooyer, T.S., Fischer, U.H., Jackson, M. and Moore, P.L. (2005). Debris-bed friction of hard-bedded glaciers. Journal of Geophysical Research 110: doi: 10.1029/2004JF000228. issn: 0148-0227. |
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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. |
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BACKGROUND DATA FILES |
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Abstract |
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Keywords
Cryosphere, Glaciers, Cryosphere, Glaciology (1621, 1827, 1863), Cryosphere, Instruments and techniques, Cryosphere, Modeling, Hydrology, Erosion, glacier, friction, sliding, measurement, model, rheology |
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Publisher
American Geophysical Union 2000 Florida Avenue N.W. Washington, D.C. 20009-1277 USA 1-202-462-6900 1-202-328-0566 service@agu.org |
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