Grounding Zone Processes at Thwaites Glacier from ICESat-2 Data and Ice-Ocean Modelling

It is now well accepted that ice shelves and grounding zones experience changes in elevation synchronous with ocean tides, atmospheric loading and other processes. Recent studies have demonstrated that tidal pumping at the grounding zone can cause a transient migration of the grounding line hundreds of meters upstream relative to the grounded zone at low tide. As the grounded edge shifts inland, ocean intrusion leads to enhanced basal melting and grounding zone retreat, as demonstrated by previous InSAR-based studies on Thwaites Glacier in the Amundsen Sea Embayment. In this work, we use ICESat 2 elevation profile data spanning the Thwaites Glacier grounding zone and demonstrate the uplift of grounding zone topography in high tides with ocean intrusion ranging from ~1–9 km inland. The uplift of surface topography in high tides and our inferred ocean intrusion underneath the ice is heterogenous both in the along-track direction and along the width of the grounding zone. This work using ICESat 2 provides evidence in support of similar InSAR-based observations of the dynamic grounding zone and permits an independent assessment of the scale and volume of ocean water intrusion underneath Thwaites Glacier.