Bathymetry of the Antarctic continental shelf and ice shelf cavities from circumpolar gravity anomalies and other data

Ice shelves around Antarctica are buttressing the discharge of glaciers into the ocean. The intensification of westerly winds pushes warm Circumpolar Deep Water (CDW) toward Antarctica’s continental shelf and into ice shelf cavities, leading to greater basal melting and causing erosion of basal ice at faster rates. This accelerated ice loss reduces the ability of ice shelves to buttress glacier flow, amplifying Antarctica’s contribution to sea level. Therefore, understanding pathways of warm CDW up to the grounding zone is crucial for projecting Antarctica's future evolution. Although extensive bathymetric mapping has been carried out in several key areas, many regions of Antarctica still lack complete or any bathymetric data (Dorschel et al., 2022), hindering our understanding of current changes and the ability to predict ice sheet future evolution. Bathymetric measurements in Antarctica are primarily conducted with icebreaking ships equipped with echo sounders, but the presence of sea ice and icebergs complicates navigation, leaving large areas uncovered. Mapping beneath ice shelves requires more advanced methods, such as seismic surveys, AUVs, or CTD from boreholes. Despite international efforts, only eight of the largest ice shelves have received sufficient coverage due to the complexity of conducting surveys in Antarctica. Free-air gravity anomalies provide insights into variations in water thickness and bedrock-sediment density beneath ice shelves. Inversions of gravity data, properly constrained by seafloor depth observations, have shown to be an effective method for mapping bathymetry at large spatial scales. In this study, we present a novel and comprehensive bathymetry of Antarctica that includes all ice shelf cavities and previously unmeasured continental shelf areas. The inversion is based on ground-based and airborne gravity measurements compiled under the International Association of Geodesy Sub-Commission (Scheinert, 2016a). Using additional data and applying an improved remove-compute-restore processing workflow, a new compilation named “AntGG2021” was created, with a resolution refined from 10 km to 5 km (Scheinert et al., 2021). The inversion process is constrained by a unique compilation of multi- and single-beam echo sounding, seismic, AUV, CTD, and seal data from the Marine Mammals Exploring the Ocean Pole to Pole project (MEOP). We calculate the inversion uncertainty by quantifying the misfit and using unseen MBES measurements for three different sectors with varying data quality. Unknown troughs with thicker ice shelf cavities are revealed in many parts of Antarctica, especially the East. The greater depths of troughs on the continental shelf and ice shelf cavities, compared to CTD measurements since 1968, imply that many glaciers are more vulnerable to ocean subsurface warming than previously thought, which may increase projections of sea level rise. Finally, we pinpoint regions still lacking observational constraints to resolve pathways for warm water, providing potential guidance on the likely location of troughs, sills, and areas of importance for future surveys. Meanwhile, the AntGG2021 bathymetry represents a step forward in improving the characterization of ocean circulation on the continental shelf and in ice shelf cavities, which will be directly useful for researchers studying ice-ocean interactions and projecting ice mass losses from Antarctica.