Marine ice-cliff instability modeling shows mixed-mode ice-cliff failure and yields calving rate parameterization

Marine ice-cliff instability could accelerate ice loss from Antarctica, and according to some model predictions could potentially contribute >1m of global mean sea level rise by 2100 at current emission rates. Regions with over-deepening basins >1km in depth (e.g., the West Antarctic Ice Sheet) are particularly susceptible to this instability, as retreat could expose increasingly tall cliffs that could exceed ice stability thresholds. Here, we use a suite of high-fidelity glacier models to improve understanding of the modes through which ice cliffs can structurally fail and derive a conservative ice-cliff failure retreat rate parameterization for ice-sheet models. Our results highlight the respective roles of viscous deformation, shear-band formation, and brittle-tensile failure within marine ice-cliff instability. Calving rates increase non-linearly with cliff height, but runaway ice-cliff retreat can be inhibited by viscous flow and back force from iceberg melange. Ice-cliff failure that leads to marine ice-cliff instability could accelerate Antarctic Ice Sheet retreat. Here, the authors use 3D glacier models to investigate ice-cliff failure, derive a retreat rate relationship, and quantify melange back force necessary to suppress ice-cliff failure.