Parameterization of basal friction near grounding lines in a one-dimensional ice sheet model

Leguy, Gunter; Asay‐Davis, Xylar; Lipscomb, William H.

doi:10.5194/tc-8-1239-2014

Cited by 69 publications

(160 citation statements)

References 48 publications

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“…For example Pattyn et al (2006) implemented a fixed size transition zone. Theoretical work for the case of sliding with cavitation (Schoof, 2005;Gagliardini et al, 2007) has also been used to develop sliding relations in models (Leguy et al, 2014;Tsai et al, 2015), though it is not clear whether the assumptions made are applicable in all real-world cases of glacier sliding. The current study does not aim to promote use of any particular sliding relation, but rather to explore a specific aspect of the sliding implementation, namely the abruptness with which basal shear stress goes to zero as the grounding line is approached.…”

Section: Basal Slidingmentioning

confidence: 99%

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

et al. 2017

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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.

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Section: Basal Slidingmentioning

confidence: 99%

“…Budd et al, 1984) and may affect the resolution requirements for successful grounding line modelling. Recent treatments of basal traction that also vanish smoothly at the grounding line include Leguy et al (2014) and Tsai et al (2015).…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2017

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“…This physically represents the hydrological connection between the subglacial system and the ocean in the transition zone [122]. The CFL condition makes marine ice sheets also more sensitive to climate perturbations because of the zero effective pressure condition at the grounding line (contrary to the WFL condition) and a greater dependence on ice thickness [77,93,122].…”

Section: Grounding Linesmentioning

confidence: 99%

Progress in Numerical Modeling of Antarctic Ice-Sheet Dynamics

Pattyn

Favier

Sun

et al. 2017

Curr Clim Change Rep

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Numerical modeling of the Antarctic ice sheet has gone through a paradigm shift over the last decade. While initially models focussed on long-time diffusive response to surface mass balance changes, processes occurring at the marine boundary of the ice sheet are progressively incorporated in newly developed state-of-the-art ice-sheet models. These models now exhibit fast, shortterm volume changes, in line with current observations of mass loss. Coupling with ocean models is currently on its way and applied to key areas of the Antarctic ice sheet. New model intercomparisons have been launched, focusing on ice/ocean interaction (MISMIP+, MISOMIP) or icesheet model initialization and multi-ensemble projections (ISMIP6). Nevertheless, the inclusion of new processes pertaining to ice-shelf calving, evolution of basal friction, and other processes, also increase uncertainties in the contribution of the Antarctic ice sheet to future sea-level rise.

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“…This limit is discussed to be a valid approximation of basal drag in the transition zone (e.g. (Leguy et al, 2014)). …”

Section: Balance Between Driving Stress and Basal Dragmentioning

confidence: 99%

Balance between driving stress and basal drag results in linearity between driving stress and basal yield stress in Antarctica's Siple Coast Ice Streams

Wohland

Albrecht

Levermann

2016

Preprint

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Abstract. Ice streams are distinct, fast-flowing regimes within ice sheets that exhibit fundamentally different characteristics as compared to the slow-moving inner parts of the ice sheets. While alongflow surface profiles of ice sheets are typically convex, some ice streams show linearly sloping or even concave surface profiles. We use observational data of the Siple Coast in Antarctica to inversely calculate membrane stresses, driving stresses and basal yield stresses based on the Shallow 5 Shelf Approximation. Herein we assume that these marine-based ice streams are isothermal and in neglecting vertical shear we assume that their flow is dominated by sliding. We find that in the Siple Coast ice streams the membrane stresses are negligible and the driving stress balances the basal drag. It follows directly that in the Coulomb limit (i.e. basal drag independent of velocity) the driving stress is linear in the basal yield stress. In addition, we find that the ice topography and the 10 basal conditions developed such that the driving stress is linear in the basal yield stress regardless of the choice of the pseudo plastic exponent in the basal drag parameterization.

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Parameterization of basal friction near grounding lines in a one-dimensional ice sheet model

Cited by 69 publications

References 48 publications

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

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

Progress in Numerical Modeling of Antarctic Ice-Sheet Dynamics

Balance between driving stress and basal drag results in linearity between driving stress and basal yield stress in Antarctica's Siple Coast Ice Streams

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