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Abstract Future projections and past reconstructions of Antarctic Ice Sheet stability and sea‐level rise depend on knowledge of continental shelf bathymetry, which controls water circulation under floating ice and interactions between the ice shelf and seafloor. We present a bathymetry model of the Venable Ice Shelf (VIS) in the Bellingshausen Sea sector from an inversion of airborne gravity data. The new model reveals troughs up to ∼1.6 km deeper than previously mapped, providing pathways for warm Circumpolar Deep Water to access the grounding line. A bathymetric high beneath the western VIS is identified as a former pinning point. From crevasse patterns in Landsat satellite imagery, we infer intermittent grounding of the ice shelf on this high since ∼1935, and we interpret these patterns as evidence of mid‐20th century ice‐shelf thinning, in addition to a regrounding between 1970 and 1988, extending the ice‐shelf thickness record beyond the satellite era. 

Abstract New geophysical data from Antarctica's Ross Embayment reveal the structure and subglacial geology of extended continental crust beneath the Ross Ice Shelf. We use airborne magnetic data from the ROSETTA‐Ice Project to locate the contact between magnetic basement and overlying sediments. We delineate a broad, segmented basement high with thin (0–500m) non‐magnetic sedimentary cover which trends northward into the Ross Sea's Central High. Before subsiding in the Oligocene, this feature likely facilitated early glaciation in the region and subsequently acted as a pinning point and ice flow divide. Flanking the high are wide sedimentary basins, up to 3700m deep, which parallel the Ross Sea basins and likely formed during Cretaceous‐Neogene intracontinental extension. NW‐SE basins beneath the Siple Coast grounding zone, by contrast, are narrow, deep, and elongate. They suggest tectonic divergence upon active faults that may localize geothermal heat and/or groundwater flow, both important components of the subglacial system.