Basal Sliding Relations Deduced from Ice-Sheet Data
Abstract The sliding law is defined as a basal boundary condition for the large-scale bulk ice flow, relating the tangential traction τ b , overburden pressure p b , and tangential velocity u b on a smoothed-out mean bed contour. This effective bed is a lower boundary viewed on the scale of the bulk...
| Published in: | Journal of Glaciology |
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| Main Authors: | , , |
| Format: | Article in Journal/Newspaper |
| Language: | English |
| Published: |
Cambridge University Press (CUP)
1984
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| Subjects: | |
| Online Access: | http://dx.doi.org/10.1017/s0022143000005864 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143000005864 |
| Summary: | Abstract The sliding law is defined as a basal boundary condition for the large-scale bulk ice flow, relating the tangential traction τ b , overburden pressure p b , and tangential velocity u b on a smoothed-out mean bed contour. This effective bed is a lower boundary viewed on the scale of the bulk ice flow and is not the physical ice/rock or sediment interface. The sliding relation reflects on the same scale the complex motion taking place in the neighbourhood of the physical interface. The isothermal steady-state ice-sheet analysis of Morland and Johnson (1980, 1982) is applied to known surface profiles from the Greenland ice sheet and Devon Island ice cap, with their corresponding mass-balance distributions, to determine τ b , p b , and u b for each case. These basal estimates are used in turn to construct, using least-squares correlation, polynomial representations for an overburden dependence λ ( p b ) in the adopted form of sliding law τ b ═ λ ( p b ) u b 1/ m with m ≥ 1. The two different data sets determine functions λ ( p b ) of very different magnitudes, reflecting very different basal conditions. A universal sliding law must therefore contain more general dependence on basal conditions, but the two relations determined appear to describe the two extremes. Hence use of both relations in turn to determine profiles compatible with given mass-balance distributions can be expected to yield extremes of the possible profiles, and further to show the sensitivity of profile form to variation of the sliding relation. The theory is designed as a basis for reconstruction of former ice sheets and their dynamics which are related to the two fundamental determinants of surface mass balance and basal boundary condition. |
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