On the pattern of WAIS retreat in eastern Ross Sea based on a regional synthesis of new geophysical and geological data acquired during NBP1502

New multibeam and seismic data acquired during NBP1502 reveal that a series of backstepping grounding zone wedges (GZWs) were constructed on the middle shelf as the West Antarctic Ice Sheet (WAIS) retreated from the Whales Deep paleo-ice stream trough. The geomorphological information provided by these geophysical data were used to acquire a regional grid of jumbo-piston and kasten cores. Here, we present our regional synthesis of the new geophysical and geological data. The distributions of upcore transitions from diamict to sub-ice-shelf facies on the outer-most shelf demonstrate that as the grounded ice retreated in four discrete backsteps, the calving front remained in the vicinity of the shelf edge, approximately 50 kilometers to the north. In contrast, the upcore transition at the fourth backstep shows GZW diamict directly overlain by open-marine facies. We interpret this to indicate that a major retreat of both grounded and floating ice was associated with the termination of the middle-shelf grounding event. The minimum retreat distance was greater than 100 kilometers.