Localized Basal Melting Near the Ross Ice Shelf Front: Interplay of Bathymetry, Ocean Heat Fluxes, and Ice Damage History

David Felton Porter, Columbia University, Lamont-Doherty Earth Observatory, Palisades, NY, United States, Kirsty J Tinto, Columbia University, Lamont-Doherty Earth Observatory, Palisades, United States, Robin Elizabeth Bell, Lamont-Doherty Earth Observatory of Columbia University, Palisades, United States, Scott R Springer, Earth & Space Research, Seattle, WA, United States, Laurence Padman, Earth & Space Research, Corvallis, United States, Helen Amanda Fricker, University of California, San Diego, Scripps Institution of Oceanography, La Jolla, CA, United States, Cyrille Mosbeux, LGGE Laboratoire de Glaciologie et Géophysique de l’Environnement, Saint Martin d'Hères, France and Indrani Das, Lamont -Doherty Earth Observatory, Palisades, NY, United States
Abstract:
Recent observations show that increased basal melt rates near the Ross Ice Shelf (RIS) front can influence ice shelf stability and the loss of grounded ice from both West and East Antarctic catchments. Ice shelf basal melt depends on complex long-term interactions between the ice base, ocean cavity, and underlying geology. To develop a better understanding of RIS stability in a changing climate, we use a combination of historical and recent observations of these along the RIS front near Roosevelt Island to demonstrate how such processes interact to determine ice shelf mass loss processes in this region. We focus on a region near Hayes bank, where mCDW flows south under the ice front; the southern extent of the sub-ice-shelf bank controls the maximum penetration of mCDW heat into the cavity. Recent radar observations from ROSETTA-Ice project mapped a 25 km wide region of thinner ice and bright reflectors consistent with basal melt. Ross Sea cruises spanning nearly four decades, near-front moorings in the 1980s, and autonomous profiling floats deployed by ROSETTA-Ice, have all collected hydrographic data near this thin-ice area, allowing for estimation of southward mCDW heat flux and identifying fresh ice shelf meltwater outflow. Circulation depends on water column thickness and therefore the relative locations of thinned ice and submarine ridges matters. New gravity-derived bathymetry from ROSETTA-Ice shows Hayes Bank extends less than 100 km under the RIS, suggesting that mCDW inflow to the west of Hayes Banks does not extend far into the back of the RIS cavity, limiting its melting potential to a small region near the front, where the ice shelf does little buttressing (Furst et al., 2016). Upstream lies Steershead Ice Rise, where re-grounding and basal shear stress impart damage that travels and evolves along flow to the front. Ocean melting interacts with damage features (e.g. transverse rifts, the longitudinal wake from Steershead), increasing calving characteristics at the front, instigating a positive feedback between thinning ice and increased access and basal melt by mCDW. Over scales of thousands of years, the permanence of these banks (i.e. depositional versus basement) shows how geology can alter the interplay between globally-sourced ocean waters and the ice sheets.
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