Matthew Siegfried (Department of Geophysics, Colorado School of Mines, Golden, CO, United States); Susan Howard (Earth and Space Research, Seattle, WA, United States); Laurie Padman (Earth and Space Research, Corvallis, OR, United States); Ellianna Abrahams (Department of Geophysics and Stanford Data Science Institute, Stanford University, Stanford, CA, United States); Tasha Snow (NASA Goddard Space Flight Center and ESSIC, University of Maryland, United States)

Southern Ocean tides impact the cryosphere and global climate system, for example altering ice shelf basal melt rates, sea ice concentration, and production of Antarctic Bottom Water. Southern Ocean tides also drive ice stream and ice shelf velocity variability on daily to monthly timescales. However, models of tides around Antarctica are less accurate than models of subpolar ocean tides, due to lack of in situ tide gauges and complications in interpreting satellite altimetry data at high latitudes. In particular, improved observations of interactions between tides and ice shelves are necessary to analyze and project the coupled tide-ice shelf system. NASA/CNES’s Surface Water and Ocean Topography (SWOT) mission is the first satellite that favorably aliases major tidal harmonics, reaches far enough south (~78°S) to provide data over several critical Antarctic ice shelves, and obtains data regardless of cloud cover. We explore the potential for SWOT elevation change data over ice shelves to improve our understanding of Antarctic tides, including accurately determining ice elevation in regions of complex topography via comparison to satellite laser altimetry data from NASA’s Ice, Cloud, and land Elevation Satellite-2 (ICESat-2) mission and identifying supraglacial water features on cloudy days via comparison to Sentinel-2 optical imagery. We demonstrate the feasibility of using SWOT to observe tides underneath ice shelves through elevation-change comparisons to ICESat-2 data and regional tide models. Accurate ice-shelf elevations are currently limited to areas covered by SWOT’s high resolution data product, which is only available over certain ice shelves since November 2024 after adjustments to the high resolution mask proposed by the SWOT Cryosphere Working Group. We discuss challenges associated with correcting the low-resolution data over ice shelves, which would lead to more extensive spatial coverage and a longer time series necessary for calculating tidal constituents. Despite these challenges, SWOT provides revolutionary new polar tide observations, important for improved understanding of tidal interactions with ice shelves and how tides impact ice stream flow.