InSAR for tide modelling in Antarctic ice-shelf grounding zones

Differential interferometric synthetic aperture radar (DInSAR) is a valueable tool to detect ice-sheet motion near Antarctica's oceanic margin. These space-borne measurements have been used extensively to map the location and retreat of ice-shelf grounding lines as an indicator for the onset of marine ice-sheet instability, to derive material properties of glacial ice as well as to improve current estimates of ice thickness along the ice-sheets' edge. The main difficulty interpreting DInSAR is that images originate from a combination of several SAR images and do not display ice deflection at the individual times of satellite data acquisition. Here, we combine the sub-centimetre accuracy and spatial benefits of DInSAR with the temporal benefits of tide models to infer the spatiotemporal dynamics of ice-ocean interaction during the satellite overpasses. We demonstrate the potential of our method with comparison of unraveled TerraSAR-X interferograms to in-situ data from both an almost stagnant ice shelf near McMurdo Station and the fast-flowing Darwin Glacier located within the Transantarctic Mountains. Applications range from improving coarsly-gridded tide models to resolve small-scale features at the spatial resolution and vertical accuracy of SAR imagery, to extracting viscoelastic signals and information about ice heterogenity and thickness from the satellite derived surface flexure. The unraveling of DInSAR into its individual components has the potential to become a standard method in grounding-zone glaciology and modelling of ocean tides. The software is coded in Python and freely-available to the open-source community on Github.