| 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 (MISMIP+ and MISMIP3d), and 10 future simulations of
West Antarctic ice retreat under RCP8.5-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 15 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. |
