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| Titel |
Temporal variations in the flow of a large Antarctic ice stream controlled by tidally induced changes in the subglacial water system |
| VerfasserIn |
S. H. R. Rosier, G. H. Gudmundsson, J. A. M. Green |
| 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 ; 9, no. 4 ; Nr. 9, no. 4 (2015-08-21), S.1649-1661 |
| Datensatznummer |
250116839
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| Publikation (Nr.) |
 copernicus.org/tc-9-1649-2015.pdf |
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| Zusammenfassung |
| Observations show that the flow of Rutford Ice Stream (RIS) is strongly
modulated by the ocean tides, with the strongest tidal response at the 14.77-day tidal period (Msf). This is striking because this period is
absent in the tidal forcing. A number of mechanisms have been proposed to
account for this effect, yet previous modelling studies have struggled to
match the observed large amplitude and decay length scale. We use a nonlinear
3-D viscoelastic full-Stokes model of ice-stream flow to investigate this
open issue. We find that the long period Msf modulation of
ice-stream velocity observed in data cannot be reproduced quantitatively
without including a coupling between basal sliding and tidally induced
subglacial water pressure variations, transmitted through a highly conductive
drainage system at low effective pressure. Furthermore, the basal sliding law
requires a water pressure exponent that is strongly nonlinear with q = 10 and
a nonlinear basal shear exponent of m = 3. Coupled model results show that
sub-ice shelf tides result in a ∼12 % increase in mean horizontal
velocity of the adjoining ice stream. Observations of tidally induced
variations in flow of ice streams provide stronger constraints on basal
sliding processes than provided by any other set of measurements. |
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