Data for: Grounding zone of Amery Ice Shelf, Antarctica, from differential synthetic-aperture radar interferometry

We employ a time series of Sentinel-1 differential radar interferometry data from year 2018 to detect the variability of the grounding line position of the Fisher, Mellor and Lambert glaciers, which drain an ice volume equivalent to an 8-m sea level rise from East Antarctica. We observe kilometer-scale tidal migration, two orders of magnitude larger than expected for ice in hydrostatic equilibrium on a hard bed. The migration is not in phase with changes in oceanic tide. In two major estuaries underlaid by subglacial channels, we observe two states of migration that switch on and off over time scales of several weeks. The range of vertical motion indicates a water column thickness of 2 to 20 centimeters. Such intrusions over wide grounding zones are not accounted for in physical models. Including wide grounding zone with vigorous melt will enhance the sensitivity of glaciers to ocean warming and increase the projections of mass loss.