Sea-ice and ice-shelf variability in the Amundsen Sea Embayment, West Antarctica

Abstract

Global sea-level rise contributed by Antarctic ice-mass loss could soon outpace all other sources. The ice-mass-loss signal of the Antarctic Ice Sheet is dominated by the Amundsen Sea Embayment (ASE) in West Antarctica. Ice shelves in the ASE influence the ice-mass-loss rates of the Antarctic Ice Sheet through their ability to buttress the grounded ice and modulate ice-flow speed. Ice shelves reduce ice flow and retreat by buttressing grounded ice. Previous studies show that sea ice can buttress ice shelves via mechanical bonding and provide protection from ocean swells. Whereas several studies have examined the trends in West Antarctic sea ice and dynamics of ice shelves in the ASE separately, the interaction between ice shelves and sea ice in the ASE is poorly understood. This study investigated the relationship between sea-ice-area (SIA) anomalies and ice-shelf velocities of three large ASE ice shelves, of Thwaites Eastern Ice Shelf (TEIS), Pine Island Glacier Ice Shelf (PIGIS) and Crosson Ice Shelf (CIS), on seasonal and monthly timescales from summer 2001-02 to 2021-22 and 2014 to 2022, respectively. SIA anomalies and ice-shelf velocities were derived from satellite remote sensing data. Sea ice in the ASE experienced four- to seven-year periods of relatively consistent positive or negative SIA anomalies. Time series of TEIS average velocity shows increased velocity in the early 2000’s, followed by relative stability, then again an increase from the late-2010’s onwards. Time series of the PIGIS average velocity shows increased velocities over the 20-year period, with consistent acceleration from the late-2010’s onwards. Time series of the CIS average velocity shows relatively stable to slightly decreasing trends over the 20-year period. Correlation analysis of sea ice and ice shelves predominantly showed no significant relationship. Fewer than 15% of Spearman’s correlation coefficients between the SIA anomalies and ice-shelf velocities were statistically significant. Therefore, results of this study indicate no apparent relationship between sea ice and ice-shelf velocity in the ASE, at least on seasonal and monthly time scales. The relationship may be more evident on an episodic basis than in a long-term record, as previous studies identified the influence of sea-ice events (i.e., sea-ice breakout or retreat) on Antarctic ice shelves on daily to weekly time scales.