Oceanic gateways to Antarctic grounding lines – Impact of critical access depths on sub-shelf melt

• Main Authors: Nicola, Lena, Reese, Ronja, Kreuzer, Moritz, Albrecht, Torsten, Winkelmann, Ricarda
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2023
• Subjects: article; Verlagsveröffentlichung; Antarc*; Antarctic; Antarctica; Ice Sheet; Ice Shelf; Ice Shelves
• Online Access: https://doi.org/10.5194/egusphere-2023-2583; https://noa.gwlb.de/receive/cop_mods_00070096; https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00068455/egusphere-2023-2583.pdf; https://egusphere.copernicus.org/preprints/2023/egusphere-2023-2583/egusphere-2023-2583.pdf

Melting underneath the floating ice shelves surrounding the Antarctic continent is a key process for the stability of the Antarctic Ice Sheet and therefore its current and future mass loss. Troughs and sills on the continental shelf play a crucial role in modulating sub-shelf melt rates, as they can allow or block the access of relatively warm, modified Circumpolar Deep Water to ice-shelf cavities. Here we identify potential oceanic gateways that could allow the access of warm water masses to Antarctic grounding lines based on critical access depths inferred from high-resolution bathymetry data. We analyse the properties of water masses that are currently present in front of the ice shelf and that might intrude into the respective ice-shelf cavities in the future. We use the ice-shelf cavity model PICO to estimate an upper limit of melt rate changes in case all warm water masses up to a certain depth level gain access to the cavities. We find that melt rates could increase in all regions at least by a factor of 2. Depending on the presence or absence of an oceanic gateway and the current ice-shelf melt conditions we find up to 200-fold larger melt rates. The identification of oceanic gateways is thus valuable for assessing the potential of ice-shelf cavities to switch from a 'cold' to a 'warm' state, which could result in widespread ice loss from Antarctica.