Thompson, J. and Simons, M. and Tsai, V. C. (2014) Modeling the elastic transmission of tidal stresses to great distances inland in channelized ice streams. Cryosphere, 8 (6). pp. 2007-2029. ISSN 1994-0416 . http://resolver.caltech.edu/CaltechAUTHORS:20140618-141557404
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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.
|Additional Information:||© 2014 Author(s). This work is distributed under the Creative Commons Attribution 3.0 License. Published by Copernicus Publications on behalf of the European Geosciences Union. Received: 21 February 2014 – Published in The Cryosphere Discuss.: 25 April 2014; Revised: 18 September 2014 – Accepted: 22 September 2014 – Published: 5 November 2014. The authors would like to thank the two anonymous reviewers of this manuscript and editor Oliver Gagliardini for their constructive comments. We would also like to thank J. N. Bassis and Martin Lüthi for their constructive review of an earlier version of this manuscript. Part of this research was carried out at the Jet Propulsion Laboratory and the California Institute of Technology under a contract with the National Aeronautics and Space Administration and funded through the President’s and Director’s Fund Program.|
|Official Citation:||Thompson, J., Simons, M., and Tsai, V. C.: Modeling the elastic transmission of tidal stresses to great distances inland in channelized ice streams, The Cryosphere, 8, 2007-2029, doi:10.5194/tc-8-2007-2014, 2014.|
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|Deposited By:||Tony Diaz|
|Deposited On:||18 Jun 2014 21:33|
|Last Modified:||23 Nov 2016 19:30|
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