Description:
<jats:p>Abstract. The use of a boundary-layer parameterization of
buttressing and ice flux across grounding lines in a two-dimensional
ice-sheet model is improved by allowing general orientations of the
grounding line. This and another modification to the model's grounding-line
parameterization are assessed in three settings: rectangular fjord-like
domains – the third Marine Ice Sheet Model Intercomparison Project (MISMIP+) and Marine Ice Sheet Model Intercomparison Project for plan view models (MISMIP3d) – and future simulations of West Antarctic
ice retreat under Representative Concentration Pathway (RCP)8.5-based climates. The new modifications are found to
have significant effects on the fjord-like results, which are now within the
envelopes of other models in the MISMIP+ and MISMIP3d intercomparisons. In
contrast, the modifications have little effect on West Antarctic retreat,
presumably because dynamics in the wider major Antarctic basins are
adequately represented by the model's previous simpler one-dimensional
formulation. As future grounding lines retreat across very deep bedrock
topography in the West Antarctic simulations, buttressing is weak and
deviatoric stress measures exceed the ice yield stress, implying that
structural failure at these grounding lines would occur. We suggest that
these grounding-line quantities should be examined in similar projections by
other ice models to better assess the potential for future structural
failure.
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