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| Titel |
Modeling the elastic transmission of tidal stresses to great distances inland in channelized ice streams |
| VerfasserIn |
J. Thompson, M. Simons, V. C. Tsai |
| 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 ; 8, no. 6 ; Nr. 8, no. 6 (2014-11-05), S.2007-2029 |
| Datensatznummer |
250116372
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| Publikation (Nr.) |
 copernicus.org/tc-8-2007-2014.pdf |
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| Zusammenfassung |
| Geodetic surveys suggest that ocean tides can modulate the motion of
Antarctic ice streams, even at stations many tens of kilometers inland from
the grounding line. These surveys suggest that ocean tidal stresses can
perturb ice stream motion at distances about an order of magnitude farther
inland than tidal flexure of the ice stream alone. Recent models exploring
the role of tidal perturbations in basal shear stress are primarily one- or
two-dimensional, with the impact of the ice stream margins either ignored or
parameterized. Here, we use two- and three-dimensional finite-element
modeling to investigate transmission of tidal stresses in ice streams and
the impact of considering more realistic, three-dimensional ice stream
geometries. Using Rutford Ice Stream as a real-world comparison, we
demonstrate that the assumption that elastic tidal stresses in ice streams
propagate large distances inland fails for channelized glaciers due to an
intrinsic, exponential decay in the stress caused by resistance at the ice
stream margins. This behavior is independent of basal conditions beneath the
ice stream and cannot be fit to observations using either elastic or
nonlinear viscoelastic rheologies without nearly complete decoupling of the
ice stream from its lateral margins. Our results suggest that a mechanism
external to the ice stream is necessary to explain the tidal modulation of
stresses far upstream of the grounding line for narrow ice streams. We
propose a hydrologic model based on time-dependent variability in till
strength to explain transmission of tidal stresses inland of the grounding
line. This conceptual model can reproduce observations from Rutford Ice Stream. |
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