Locating subglacial sediments across West Antarctica with isostatic gravity anomalies

Subglacial sediments are an important control on fast flowing ice in West Antarctica but their spatial distribution over catchment-wide areas is still largely unknown. Previously, airborne gravity anomalies could not clearly image sedimentary basins beneath the ice because broad, crustal-scale gravity signals masked the nearsurface anomalies. We show here that it is possible to use additional processing to produce an isostatic gravity anomaly, which is sensitive to the locations of sedimentary basins. Our results reveal that the inferred major basin beneath Thwaites Glacier is confined to the Byrd Subglacial Basin, but that there are also basins underlying the onset of tributary fast flow. In the Ross Sea Embayment, known sedimentary basins coincide with negative isostatic anomalies. The sedimentary basins beneath the Ross Sea Embayment ice streams are more widespread and likely have a greater sediment thickness than the basins beneath Thwaites Glacier in the Amundsen Sea Embayment.