Comparison of the regional gravity-anomaly fields measured at the surface with the low-order terms of the Goddard Earth Model (GEM) series of satellite-derived gravity fields shows close agreement near the edge of the Ross Sea continental shelf, and a departure of the surface gravity field from the regional satellite-determined field that becomes increasingly negative in a grid-northerly direction. We assume the deviation to be the result of crustal depression remaining from former ice loading, and calculate that a crustal depression of 0 to 190 m remains along a grid-south-east to north-west transect through the Ross embayment.
An estimated 50 to 170 m of crustal uplift remains unadjusted in the grid-western part of the present Ross Ice Shelf, assuming a particular initialice load at 18 ka BP (CLIMAP) and a simple exponent ial model of crustaluplift. The approximate agreement between the two methods has encouraged us to use the crustal up - lift estimated from the gravity field and a simple exponential model of crustal rebound to test models of past ice loading and retreat models. Preliminary results show agreement with the CLIMAP reconstruction of the 18 ka BP West Antarctic ice sheet and a retreat model similar to that of Reference Thomas and BentleyThomas and Bentley (1978).