Mapping ice grounding zones using elevation changes from CryoSat-2 swath-processed interferometric mode data

Abstract

Ongoing loss of ice mass in the Amundsen Sea Embayment of West Antarctica has the potential to contribute significantly to sea level rise. Ice grounding lines are important in understanding the glacial dynamics driving these changes, and satellite remote sensing methods have provided information about grounding line location. However, limitations of existing methods for identifying grounding zone features include difficulty mapping in regions with fast-moving ice, where grounding line retreat has been most pronounced. This study aimed to demonstrate a novel approach for mapping grounding zone features that is effective for fast flowing ice where thinning is present. Elevation changes from CryoSat-2 swath-processed interferometric mode data from April 2010-January 2022 were examined to explore grounding zone dynamics in the Amundsen Sea Embayment. Grounding zone boundaries mapped using 10-year elevation change data were in general agreement with existing grounding zone datasets, and grounding zones mapped from 5-year elevation change data provided insights about grounding zone retreat that guided further analyses. Pixel-scale timeseries analyses of monthly elevation revealed two main periods in which ice transitioned from grounded to floating, January to April 2014 and July to October 2016, suggesting grounding line retreat. The spatial patterns of this transition match those of existing grounding zone datasets. Onset of accelerated ice thinning was also identified in two periods: October 2012-January 2014 and January 2017-January 2018. These investigations demonstrate that rate of elevation change from swath-processed CryoSat-2 data provides useful information in contribution to grounding zone investigations, and provide a foundation for further refinement.