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

Anna J. Crawford,Thomas Zwinger,Douglas I. Benn,Joe Todd,Jan A. Åström,Jeremy N. Bassis

doi:10.1038/s41467-021-23070-7

Abstract

Marine ice-cliff instability could accelerate ice loss from Antarctica, and according to some model predictions could potentially contribute >1 m of global mean sea level rise by 2100 at current emission rates. Regions with over-deepening basins >1 km 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 mélange.

Highlights

Marine ice-cliff instability could accelerate ice loss from Antarctica, and according to some model predictions could potentially contribute >1 m of global mean sea level rise by 2100 at current emission rates
The importance of clarifying whether Marine ice-cliff instability (MICI) will materialise is demonstrated by ice-sheet model output showing enhanced and alarming rates of global mean sea-level rise (SLR) when ice-cliff failure is represented with a simple parameterization in models of the Antarctic Ice Sheet[1]
HiDEMbe is used to simulate the predominantly tensile failure of glaciers, whereas HiDEMve is designed to simultaneously model viscous deformation and fracture in a simplified form by partly decreasing or weakening the elastic-brittle bond connections while compensating with a short-range cohesive force that allows for viscous shear deformation

Summary

Introduction

Marine ice-cliff instability could accelerate ice loss from Antarctica, and according to some model predictions could potentially contribute >1 m of global mean sea level rise by 2100 at current emission rates. The time to failure (TtF; d), retreat magnitude (R; m) and calving retreat rate (Ĉ; m d−1) found with the Elmer/Ice–HiDEMbe (the brittle-elastic version of the Helsinki Discrete Element Model) workflow over the range of susceptible ice thicknesses with varying ice temperature (Tice) and basal slip conditions.

Results

Conclusion