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.
VAW, Eidgenössische Technische Hochschule Zürich, ETHZ, Zürich, Switzerland; Antarctic Climate and Ecosystems Cooperative Research Centre, University of Tasmania, Hobart, Australia; Arctic Centre, University of Lapland, Rovaniemi, Finland; Australian Antarctic Division, Kingston, TAS, Australia; Univ. Grenoble Alpes, CNRS, IRD, IGE, Grenoble, France; CSC-IT Center for Science Ltd., Espoo, Finland; Institute of Low Temperature Science, Hokkaido University, Sapporo, Japan
Recommended Citation:
Michael Gladstone R,, Charles Warner R,, Keith Galton-Fenzi B,et al. Marine ice sheet model performance depends on basal sliding physics and sub-shelf melting[J]. Cryosphere,2017-01-01,11(1)