Modeling the deformation regime of Thwaites Glacier, West Antarctica, using a simple flow relation for ice anisotropy (ESTAR)
Ice deformation dominates the evolution of ice shelf flow and the slow-moving regions in theinterior of ice sheets. However, deformation may be poorly represented in large-scale ice sheet models thatuse the Glen flow relation, due to its questionable applicability to the steady-state flow of anisotr...
| Published in: | Journal of Geophysical Research: Earth Surface |
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| Main Authors: | , , , , , |
| Format: | Article in Journal/Newspaper |
| Language: | English |
| Published: |
Wiley-Blackwell Publishing Inc.
2022
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| Subjects: | |
| Online Access: | https://doi.org/10.1029/2021JF006332 http://ecite.utas.edu.au/154118 |
| Summary: | Ice deformation dominates the evolution of ice shelf flow and the slow-moving regions in theinterior of ice sheets. However, deformation may be poorly represented in large-scale ice sheet models thatuse the Glen flow relation, due to its questionable applicability to the steady-state flow of anisotropic icethat prevails in ice sheets, having been derived from secondary creep rates of isotropic ice. We assess thedeformation regimes of Thwaites Glacier, West Antarctica, using the Glen and Empirical Scalar TertiaryAnisotropy Regime, (ESTAR) flow relations, the latter being derived from steady-state deformation rates ofanisotropic ice. For grounded ice, the character of the flow relation determines the contribution of deformationto overall flow, with ESTAR producing greater bed-parallel shear deformation than the standard Glen flowrelation. The ESTAR experiments show larger basal shear stress maxima than the standard Glen experimentbecause ESTAR treats the responses to simple shear stresses and compression stresses differently, reducingthe role of lateral and longitudinal stresses in momentum balance. On the Thwaites Glacier Tongue, ESTARprovides the best match to observed speeds by accounting for the differing effects of stresses on ice flow. Ourresults highlight the importance of the numerical description of anisotropy, particularly: In regions of transitionfrom deformation-dominated to sliding-dominated flow; in the approach to the grounding line, and acrossice shelves. Given the importance of these locations in determining mass flux into the ocean, our results haveimplications for projections of sea level change from Antarctic ice loss. |
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