Ice shelf stability and glacial history in coastal Dronning Maud Land, East Antarctica

<p>Topographic data sets in and around Antarctica have covered increasingly more ground over recent years and decades. While shipborne hydroacoustic data deliver seafloor information at and beyond the ice shelves’ calving fronts, ice penetrating radar data provide bedrock information beneath grounded ice sheets. The seafloor beneath the interjacent ice shelves, however, is largely unexplored and its unveiling by seismic reflection data is linked with tremendous logistical efforts. A lack of knowledge regarding topographic boundary conditions in these crucial coastal regions has not only hindered proper assessments of water mass and heat exchange between the open ocean and ice shelf cavities, but also an interpretation of glaciodynamic and geomorphological processes in their entirety.</p><p>We have modelled the subglacial bathymetry for the majority of ice shelves at the coast of Dronning Maud Land in East Antarctica from 10º W to 35º E by inverting topographic signals in airborne gravity data and tying them to existing acoustic and radar soundings. Our models cover the Ekström, Atka, Jelbart, Fimbul, Vigrid, Nivl, Borchgrevink, and Roi Baudouin ice shelves. Recurring bathymetric patterns beneath the ice shelves are linked back to their shared regional setting. Deep troughs that mimic present-day ice flow are confined landward by grounding lines and seaward by shallow bathymetric sills at or close to the continental shelf break. These sills and further minor ridges crossing the troughs and continental shelves run perpendicular to current ice flow and were likely formed at paleo-grounding lines over previous glacial cycles.</p><p>The shallow bathymetric sills along the shelf breaks are crossed by narrow gateways. Although deeper than the sill crests, the floors of these gateways mostly still lie above or at the average depth of the Warm Deep Water thermocline off coastal Dronning Maud Land. Hence, warm and deep water intrusion into the ice shelf cavities of Dronning Maud Land is currently likely to be limited and sporadic. The depths of the gateways are, however, critical for an understanding of future risk to ice shelf stability in Dronning Maud Land in response to thermocline shallowing during oceanographic change.</p>