The Ellsworth Subglacial Highlands: Inception and retreat of the West Antarctic Ice Sheet

Antarctic subglacial highlands are where the Antarctic ice sheets first developed and the 'pinning points' where retreat phases of the marine-based sectors of the ice sheet are impeded. Due to low ice velocities and limited present-day change in the ice sheet interior, West Antarctic subglacial highlands have been overlooked for detailed study. These regions have considerable potential, however, for establishing from where the West Antarctic Ice Sheet (WAIS) originated and grew, and its likely response to warming climates. Here, we characterize the subglacial morphology of the Ellsworth Subglacial Highlands (ESH), West Antarctica, from ground-based and aerogeophysical radio-echo sounding (RES) surveys and the MODIS Mosaic of Antarctica. We document well-preserved classic landforms associated with restricted, dynamic,
marine-proximal alpine glaciation, with hanging tributary valleys feeding a significant overdeepened trough (the Ellsworth Trough) cut by valley (tidewater) glaciers. Fjordmouth threshold bars down-ice of two overdeepenings define both the northwest and southeast termini of paleo outlet-glaciers which cut and occupied the Ellsworth Trough. Satellite imagery reveals numerous other glaciated valleys, terminating at the edge of deep former marine basins (e.g. Bentley Subglacial Trench), throughout ESH. These geomorphic data can be used to reconstruct the glaciology of the ice masses that formed the proto-WAIS. The landscape predates the present ice sheet, and was formed by a small dynamic ice-field(s), similar to those of the present-day Antarctic Peninsula, at times when the marine sections of the WAIS were absent. ESH represents a major seeding centre of the paleo-WAIS, and its margins represent the pinning point at which future retreat of the marine-based WAIS would be arrested.