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| Titel |
Analytical solutions for the surface response to small amplitude perturbations in boundary data in the shallow-ice-stream approximation |
| VerfasserIn |
G. H. Gudmundsson |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1994-0416
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| Digitales Dokument |
URL |
| Erschienen |
In: The Cryosphere ; 2, no. 2 ; Nr. 2, no. 2 (2008-07-16), S.77-93 |
| Datensatznummer |
250000526
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| Publikation (Nr.) |
 copernicus.org/tc-2-77-2008.pdf |
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| Zusammenfassung |
| New analytical solutions describing the effects of small-amplitude
perturbations in boundary data on flow in the shallow-ice-stream
approximation are presented. These solutions are valid for a
non-linear Weertman-type sliding law and for Newtonian ice rheology.
Comparison is made with corresponding solutions of the
shallow-ice-sheet approximation, and with solutions of the full Stokes
equations. The shallow-ice-stream approximation is commonly used to
describe large-scale ice stream flow over a weak bed, while the
shallow-ice-sheet approximation forms the basis of most current
large-scale ice sheet models. It is found that the shallow-ice-stream
approximation overestimates the effects of bed topography
perturbations on surface profile for wavelengths less than about 5 to
10 ice thicknesses, the exact number depending on values of surface
slope and slip ratio. For high slip ratios, the shallow-ice-stream
approximation gives a very simple description of the relationship
between bed and surface topography, with the corresponding transfer
amplitudes being close to unity for any given wavelength. The
shallow-ice-stream estimates for the timescales that govern the
transient response of ice streams to external perturbations are
considerably more accurate than those based on the shallow-ice-sheet
approximation. In particular, in contrast to the shallow-ice-sheet
approximation, the shallow-ice-stream approximation correctly
reproduces the short-wavelength limit of the kinematic phase speed
given by solving a linearised version of the full Stokes system. In
accordance with the full Stokes solutions, the shallow-ice-sheet
approximation predicts surface fields to react weakly to spatial
variations in basal slipperiness with wavelengths less than about 10
to 20 ice thicknesses. |
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