Tidally forced bending of the Thwaites glacier grounding zone and implications for seawater pumping

Abstract:

Floating ice shelves flex with ocean tides. Viscoelastic beam models have predicted that this tidal flexure extends some distance upstream into grounded ice, potentially pumping seawater across the grounding zone. Here we present the first-ever observations (we believe) of grounded ice bending at tidal frequencies. Tiltmeters deployed across the grounding zone of Thwaites glacier show a negative correlation of along-flow tilt with tides for ~1km inland of the grounding zone and a positive correlation farther upglacier. This inland bending likely pumps seawater across the Thwaites grounding zone by creating alternating low and high pressure zones that receive and trap seawater. Our results provide a physical justification for ice-ocean models to include some degree of ocean-forced melt inland of the grounding zone while also placing geographic limits on the inland influence of tidal pumping.