A susceptibility index for ice shelf disintegration due to sea ice loss and swell impacts

Antarctic ice shelves reduce the rate at which the Antarctic Ice Sheet flows into the ocean. Thus, the deteriorating state of many ice shelves threatens an acceleration in global sea level rise, which is a major consideration for adaptation policies in countries worldwide. Weakening of ice shelves is compounded by loss of surrounding sea ice (the frozen ocean surface), which allows powerful ocean waves to reach ice shelves and hasten the breaking away of large chunks of ice shelves in a process known as "calving". We conducted case studies and large-scale assessments of the ice shelf–sea ice–ocean wave system, generating new datasets and models that allowed us to understand the thresholds reached in large-scale calving events and predict the susceptibility of ice shelves to future calving events. The project outputs and outcomes are now available to end-user and policy makers for advanced assessments of future ice shelf losses that inform sea level rise projections.

The project has achieved advances on two fronts. (1) New mathematical models of wave-induced ice shelf vibrations have been developed, in which the shelf is modelled as a finite elastic body rather than a thin plate, allowing for more accurate modelling of stresses around rifts and other defects in the shelves, and with BEDMAP2 data integrated for the ice shelf thickness and seabed profiles. The model developments and results have been published in a series of journal articles and presented at domestic and international research conferences. The code has been made freely available in a GitHub repository. (2) Satellite-derived sea ice concentration datasets have been used to calculate open ocean corridors leading to shelves over the past four decades, and the team have begun integrating the corridors with ocean wave hindcast datasets to calculate wave energy reaching the shelves, and determine long-term trends. Preliminary results have been presented at a domestic conference and at a research seminar.

The team have generated a data product giving daily time series of Antarctic coastline without a sea ice barrier, during the Satellite era (1979–). An HDR student has joined the team, and is currently extending the data product using a wave hindcast to generate a time series of coastline exposed to ocean waves. Moreover, the team have developed the first mathematical model of ice shelf vibrations induced by open ocean waves, in which the shelf is modelled using the full equations of elasticity, and permits ice thickening and seabed shoaling in the sub-shelf cavity. We have been awarded funding for a workshop on the Mathematics of Sea Ice and Ice Sheets, which we plan to hold in 2021, and bring leading international researchers in the field to Australia.