Short and Long-term Grounding Zone Dynamics of Amery Ice Shelf, East Antarctica

Abstract. The detection of grounding line (GL) positions in Antarctica is crucial for investigating the stability and health of ice sheets and glaciers. In reality the GL position is not fixed and will migrate upstream or downstream in response to varying tidal states on an hourly to daily timescale, or in response to longer-term ice dynamic change. However, the magnitude of short and long-term GL migration is not well characterised in many parts of Antarctica. In this study, we employ the Differential Range Offset Tracking method to measure the tidal GL migration on the Amery Ice Shelf in East Antarctica. We delineate 32 GL positions for the year 2021, covering 1,172 km of coastline. The results show that GL migration in this region is not solely dictated by tide amplitude but is also significantly influenced by ice velocity and subglacial bed topography, providing new insights into the GL dynamics of the region. We also observe significant long-term GL retreat in the eastern part of the Amery Ice Shelf relative to the MEaSUREs Antarctic GL derived from 2000 SAR imagery, with the maximum retreat reaching up to 10 km. Our findings underscore the need for continuous, high-resolution GL monitoring around the whole Antarctic coastline, to improve predictive models of ice sheet responses to climate changes and their subsequent impact on global sea-level rise.