Ocean circulation beneath ice shelves and associated rates of melting and freezing are influenced strongly by water column thickness and depth. The shape of the cavity beneath the Amery Ice Shelf is important for our understanding of ice shelf stability and freshwater input to the ocean and their dependence on climate. New seismic surveys of the centre region of the Amery Ice Shelf and ice-draft ... data taken at the grounding line has provided a considerable amount of new water-column thickness and bathymetry data. The data is adjusted in the unknown region south of 71 degrees 35 minutes S by comparing the complex error between simulated tides against in situ GPS observations. A finite element, hydrodynamic ocean tide model is used to simulate the 4 major constituents (S2, M2, K1 and O1). The new data differs from a previous bathymetry map in a number of places. Significantly, there is channel that leads from the Prydz bay depression into the deepest part of the AIS cavity in the south through a series of depressions. This technique has particular application when the water column beneath ice shelves is inaccessible and in situ GPS data is available.