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Volume 12, issue 10 | Copyright
The Cryosphere, 12, 3229-3242, 2018
https://doi.org/10.5194/tc-12-3229-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 09 Oct 2018

Research article | 09 Oct 2018

Grounding-line flux formula applied as a flux condition in numerical simulations fails for buttressed Antarctic ice streams

Ronja Reese1,2, Ricarda Winkelmann1,2, and G. Hilmar Gudmundsson3 Ronja Reese et al.
  • 1Potsdam Institute for Climate Impact Research (PIK), Member of the Leibniz Association, P.O. Box 60 12 03, 14412 Potsdam, Germany
  • 2University of Potsdam, Institute of Physics and Astronomy, Karl-Liebknecht-Str. 24–25, 14476 Potsdam, Germany
  • 3Department of Geography and Environmental Sciences, Northumbria University, Newcastle upon Tyne, NE1 8ST, UK

Abstract. Currently, several large-scale ice-flow models impose a condition on ice flux across grounding lines using an analytically motivated parameterisation of grounding-line flux. It has been suggested that employing this analytical expression alleviates the need for highly resolved computational domains around grounding lines of marine ice sheets. While the analytical flux formula is expected to be accurate in an unbuttressed flow-line setting, its validity has hitherto not been assessed for complex and realistic geometries such as those of the Antarctic Ice Sheet. Here the accuracy of this analytical flux formula is tested against an optimised ice flow model that uses a highly resolved computational mesh around the Antarctic grounding lines. We find that when applied to the Antarctic Ice Sheet the analytical expression provides inaccurate estimates of ice fluxes for almost all grounding lines. Furthermore, in many instances direct application of the analytical formula gives rise to unphysical complex-valued ice fluxes. We conclude that grounding lines of the Antarctic Ice Sheet are, in general, too highly buttressed for the analytical parameterisation to be of practical value for the calculation of grounding-line fluxes.

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Accurately representing grounding-line flux is essential for modelling the evolution of the Antarctic Ice Sheet. Currently, in some large-scale ice-flow modelling studies a condition on ice flux across grounding lines is imposed using an analytically motivated parameterisation. Here we test this expression for Antarctic grounding lines and find that it provides inaccurate and partly unphysical estimates of ice flux for the highly buttressed ice streams.
Accurately representing grounding-line flux is essential for modelling the evolution of the...
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