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Modeling the deformation regime of Thwaites Glacier, West Antarctica, using a simple flow relation for ice anisotropy (ESTAR)


McCormack, FS and Warner, RC and Seroussi, H and Dow, CF and Roberts, JL and Treverrow, A, Modeling the deformation regime of Thwaites Glacier, West Antarctica, using a simple flow relation for ice anisotropy (ESTAR), Journal of Geophysical Research-Earth Surface, 127, (3) Article e2021JF006332. ISSN 2169-9003 (2022) [Refereed Article]

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Copyright Statement

2022. The Authors. This article is distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) License ( which permits non-commercial use, reproduction and distribution of the work without further permission provided the original work is attributed.

DOI: doi:10.1029/2021JF006332


Ice deformation dominates the evolution of ice shelf flow and the slow-moving regions in the interior of ice sheets. However, deformation may be poorly represented in large-scale ice sheet models that use the Glen flow relation, due to its questionable applicability to the steady-state flow of anisotropic ice that prevails in ice sheets, having been derived from secondary creep rates of isotropic ice. We assess the deformation regimes of Thwaites Glacier, West Antarctica, using the Glen and "Empirical Scalar Tertiary Anisotropy Regime", (ESTAR) flow relations, the latter being derived from steady-state deformation rates of anisotropic ice. For grounded ice, the character of the flow relation determines the contribution of deformation to overall flow, with ESTAR producing greater bed-parallel shear deformation than the standard Glen flow relation. The ESTAR experiments show larger basal shear stress maxima than the standard Glen experiment because ESTAR treats the responses to simple shear stresses and compression stresses differently, reducing the role of lateral and longitudinal stresses in momentum balance. On the Thwaites Glacier Tongue, ESTAR provides the best match to observed speeds by accounting for the differing effects of stresses on ice flow. Our results highlight the importance of the numerical description of anisotropy, particularly: In regions of transition from deformation-dominated to sliding-dominated flow; in the approach to the grounding line, and across ice shelves. Given the importance of these locations in determining mass flux into the ocean, our results have implications for projections of sea level change from Antarctic ice loss.

Item Details

Item Type:Refereed Article
Keywords:ice deformation, ice sheets, glacial ice
Research Division:Earth Sciences
Research Group:Physical geography and environmental geoscience
Research Field:Glaciology
Objective Division:Environmental Management
Objective Group:Management of Antarctic and Southern Ocean environments
Objective Field:Antarctic and Southern Ocean ice dynamics
UTAS Author:McCormack, FS (Dr Felicity McCormack)
UTAS Author:Warner, RC (Dr Roland Warner)
ID Code:154118
Year Published:2022
Web of Science® Times Cited:1
Deposited By:Australian Antarctic Program Partnership
Deposited On:2022-10-31
Last Modified:2022-11-30
Downloads:5 View Download Statistics

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