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Marine ice sheet model performance depends on basal sliding physics and sub-shelf melting

Citation

Gladstone, RM and Warner, RC and Galton-Fenzi, BK and Gagliardini, O and Zwinger, T and Greve, R, Marine ice sheet model performance depends on basal sliding physics and sub-shelf melting, Cryosphere, 11, (1) pp. 319-329. ISSN 1994-0416 (2017) [Refereed Article]


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DOI: doi:10.5194/tc-11-319-2017

Abstract

Computer models are necessary for understanding and predicting marine ice sheet behaviour. However, there is uncertainty over implementation of physical processes at the ice base, both for grounded and floating glacial ice. Here we implement several sliding relations in a marine ice sheet flow-line model accounting for all stress components and demonstrate that model resolution requirements are strongly dependent on both the choice of basal sliding relation and the spatial distribution of ice shelf basal melting.

Sliding relations that reduce the magnitude of the step change in basal drag from grounded ice to floating ice (where basal drag is set to zero) show reduced dependence on resolution compared to a commonly used relation, in which basal drag is purely a power law function of basal ice velocity. Sliding relations in which basal drag goes smoothly to zero as the grounding line is approached from inland (due to a physically motivated incorporation of effective pressure at the bed) provide further reduction in resolution dependence.

A similar issue is found with the imposition of basal melt under the floating part of the ice shelf: melt parameterisations that reduce the abruptness of change in basal melting from grounded ice (where basal melt is set to zero) to floating ice provide improved convergence with resolution compared to parameterisations in which high melt occurs adjacent to the grounding line.

Thus physical processes, such as sub-glacial outflow (which could cause high melt near the grounding line), impact on capability to simulate marine ice sheets. If there exists an abrupt change across the grounding line in either basal drag or basal melting, then high resolution will be required to solve the problem. However, the plausible combination of a physical dependency of basal drag on effective pressure, and the possibility of low ice shelf basal melt rates next to the grounding line, may mean that some marine ice sheet systems can be reliably simulated at a coarser resolution than currently thought necessary.

Item Details

Item Type:Refereed Article
Keywords:marine ice sheets, ice basal sliding relations, ice shelf melting
Research Division:Earth Sciences
Research Group:Physical Geography and Environmental Geoscience
Research Field:Glaciology
Objective Division:Expanding Knowledge
Objective Group:Expanding Knowledge
Objective Field:Expanding Knowledge in the Earth Sciences
Author:Gladstone, RM (Mr Rupert Gladstone)
Author:Warner, RC (Dr Roland Warner)
Author:Galton-Fenzi, BK (Dr Ben Galton-Fenzi)
ID Code:122481
Year Published:2017
Web of Science® Times Cited:1
Deposited By:CRC-Antarctic Climate & Ecosystems
Deposited On:2017-11-15
Last Modified:2017-11-16
Downloads:0

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