Grounding Zone Ice Thickness from Satellite: Inverse Modelling of Tidal Bending

Ice shelves and outlet glaciers around Antarctica are subjected to periodic forces associated with ocean tides. Vertical motion of the ice in response to these tides varies spatially across the grounding zone region where the ice shelves are supported by the land. This vertical displacement can be measured using Interferometric Synthetic Aperture Radar (InSAR) from satellite by comparing multiple interferograms with different tidal displacements. This differential method has been widely applied to mapping the location of the grounding line. Finite element modelling shows that the tidal response can be well simulated if ice thickness and internal ice properties are well-constrained. Here we discuss a new inverse modelling optimization approach, using spatial patterns of ice flexure derived from differential interferograms to calculate ice thickness in the grounding zone. Sensitivity analyses are conducted for synthetic ice profiles in 1 and 2 dimensions. The method is then applied to glaciers and ice rises in Antarctica with results compared to ice penetrating radar measurements of thickness. This method improves current estimates of grounding zone ice thickness based on hydrostatic equilibrium assumptions and, where independent thickness estimates and multiple interferograms exist, allows an analysis of internal ice properties and temporal response to induced stresses.