InSAR-derived grounding features of the Amery Ice Shelf, East Antarctica

Differential SAR interferometry has the potential to delineate the location of the grounding lines of the Antarctic ice shelves, at unprecedented resolution. Using the available ERS SAR data, we have mapped 50-60% of the Amery Ice Shelf grounding zone. Usually the location of the grounding zone determined from SAR with this technique is identified based on the fringes which correspond to the limit of flexing of ice due to ocean tidal effects. However in one interferogram we show that the tidal contribution to the signal is small and instead, changes in sea level caused by changing atmospheric pressure (the "inverse barometer effect") make up most of the signal. In this interferogram we identify an ephemeral grounding point close to the eastern margin, and calculate the water column thickness there. In addition we discuss field measurements to be made on the ice shelf to help further interpret further the features we observe in the interferograms. In the southern limit of the grounding zone, we compare the location given by SAR with that from a hydrostatic assessment using ERS radar altimetry and airborne radio-echo sounding data.