EGUsphere EGUsphere EGUsphere EGUsphere Copernicus Publications Göttingen, Germany 10.5194/egusphere-2025-4069 Disentangling uncertainty in ISMIP6 Antarctic sub-shelf melting and 2300 sea level rise projections Beckmann Johanna https://orcid.org/0000-0002-6862-6478 1 Reese Ronja https://orcid.org/0000-0001-7625-040X 2 McCormack Felicity S. https://orcid.org/0000-0002-2324-2120 1 Cook Sue https://orcid.org/0000-0001-9878-4218 3 Bird Lawrence https://orcid.org/0000-0001-6541-2768 1 Gwyther Dawid https://orcid.org/0000-0002-7218-2785 4 Richards Daniel 5 6 Scheiter Matthias 5 Wang Yu https://orcid.org/0000-0001-9070-6004 3 Seroussi Hélène https://orcid.org/0000-0001-9201-1644 7 Abe‐Ouchi Ayako https://orcid.org/0000-0003-1745-5952 8 Albrecht Torsten https://orcid.org/0000-0001-7459-2860 9 10 Alvarez‐Solas Jorge https://orcid.org/0000-0002-2969-0442 11 12 Asay‐Davis Xylar S. https://orcid.org/0000-0002-1990-892X 13 Barre Jean‐Baptiste 14 Berends Constantijn J. https://orcid.org/0000-0002-2961-0350 15 Bernales Jorge 15 Blasco Javier https://orcid.org/0000-0001-5898-5904 16 Caillet Justine 17 7 Chandler David M. https://orcid.org/0000-0001-5759-2412 18 Coulon Violaine https://orcid.org/0000-0003-2683-7434 19 Cullather Richard 20 Dumas Christophe 21 Galton‐Fenzi Benjamin K. https://orcid.org/0000-0003-1404-4103 3 22 Garbe Julius https://orcid.org/0000-0003-3140-3307 9 23 Gillet‐Chaulet Fabien https://orcid.org/0000-0001-6592-3840 17 Gladstone Rupert https://orcid.org/0000-0002-1582-3857 24 Goelzer Heiko https://orcid.org/0000-0002-5878-9599 18 Golledge Nicholas R. https://orcid.org/0000-0001-7676-8970 25 Greve Ralf https://orcid.org/0000-0002-1341-4777 26 27 Gudmundsson G. Hilmar https://orcid.org/0000-0003-4236-5369 2 Han Holly Kyeore 13 28 Hillebrand Trevor R. https://orcid.org/0000-0003-3535-1540 13 Hoffman Matthew J. https://orcid.org/0000-0001-5076-0540 13 Huybrechts Philippe https://orcid.org/0000-0003-1406-0525 29 Jourdain Nicolas C. https://orcid.org/0000-0002-1372-2235 17 Klose Ann Kristin https://orcid.org/0000-0003-4043-7357 9 23 Langebroek Petra M. https://orcid.org/0000-0002-1246-8781 18 Leguy Gunter R. https://orcid.org/0000-0002-9963-8076 30 Lipscomb William H. https://orcid.org/0000-0002-7100-3730 30 Lowry Daniel P. https://orcid.org/0000-0002-9668-0850 31 Mathiot Pierre 17 Montoya Marisa 11 12 Morlighem Mathieu https://orcid.org/0000-0001-5219-1310 32 Nowicki Sophie https://orcid.org/0000-0001-6328-5590 33 Pattyn Frank https://orcid.org/0000-0003-4805-5636 19 Payne Antony J. https://orcid.org/0000-0001-8825-8425 34 Pelle Tyler https://orcid.org/0000-0002-9772-1730 35 Quiquet Aurélien https://orcid.org/0000-0001-6207-3043 21 Robinson Alexander https://orcid.org/0000-0003-3519-5293 11 16 Saraste Leopekka 36 Simon Erika G. 20 Sun Sainan https://orcid.org/0000-0002-1614-2658 2 Twarog Jake P. 7 Trusel Luke D. https://orcid.org/0000-0002-7792-6173 37 Urruty Benoit https://orcid.org/0000-0002-7831-0215 17 Van Breedam Jonas https://orcid.org/0000-0003-1504-9520 29 van de Wal Roderik S. W. 15 38 39 Zhao Chen https://orcid.org/0000-0003-0368-1334 3 Zwinger Thomas https://orcid.org/0000-0003-3360-4401 36 Securing Antarctica’s Environmental Future, School of Earth, Atmosphere & Environment, Monash University, Clayton, Kulin Nations, Victoria, Australia Northumbria University, Newcastle, UK Australian Antarctic Program Partnership, Institute for Marine and Antarctic Studies, University of Tasmania, Nipaluna / Hobart, Lutruwita / Tasmania, Australia School of Earth and Environmental Sciences, The University of Queensland, St Lucia, Queensland, Australia Australian Centre for Excellence in Antarctic Science, Institute for Marine and Antarctic Studies, University of Tasmania, Nipaluna / Hobart, Lutruwita / Tasmania, Australia British Antarctic Survey, Cambridge, England, UK Thayer School of Engineering, Dartmouth College, Hanover, NH, USA Atmosphere and Ocean Research Institute, University of Tokyo, Kashiwa, Japan Potsdam Institute for Climate Impact Research (PIK), Member of the Leibniz Association, Potsdam, Germany Department of Integrative Earth System Science, Max Planck Institute of Geoanthropology, Kahlaische Str. 10, 07745 Jena, Germany Departamento de Física de la Tierra y Astrofísica, Facultad de Ciencias Físicas, Universidad Complutense de Madrid, Madrid, Spain Instituto de Geociencias, Consejo Superior de Investigaciones Científicas, Universidad Complutense de Madrid, Madrid, Spain Fluid Dynamics and Solid Mechanics Group, Los Alamos National Laboratory, Los Alamos, NM, USA Department of Earth System Science, University of California Irvine, Irvine, CA, USA Institute for Marine and Atmospheric Research Utrecht, Utrecht University, Utrecht, The Netherlands Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Potsdam, Germany Univ. Grenoble Alpes/CNRS/INRAE/IRD/G-INP, Institut des Géosciences de l’Environnement, Grenoble, France NORCE Norwegian Research Centre, Bjerknes Centre for Climate Research, Bergen, Norway Laboratoire de Glaciologie, Université libre de Bruxelles, Brussels, Belgium NASA Goddard Space Flight Center, Greenbelt, MD, USA Laboratoire des Sciences du Climat et de l’environnement, LSCE-IPSL, CEA-CNRS-UVSQ, Université Paris-Saclay, Paris, France Australian Antarctic Division, Kingston, Tasmania, Australia Institute of Physics and Astronomy, University of Potsdam, Potsdam, Germany Arctic Centre, University of Lapland, Rovaniemi, Finland Antarctic Research Centre, Victoria University of Wellington, Wellington, New Zealand Institute of Low Temperature Science, Hokkaido University, Sapporo, Japan Arctic Research Center, Hokkaido University, Sapporo, Japan Earth Surface and Interior Group, Jet Propulsion Laboratory, Pasadena, CA, USA Earth System Science & Departement Geografie, Vrije Universiteit Brussel, Brussels, Belgium Climate and Global Dynamics Laboratory, NSF National Center for Atmospheric Research, Boulder, CO, USA GNS Science, Lower Hutt, New Zealand Department of Earth Sciences, Dartmouth College, Hanover, NH, USA Department of Geology, University at Buffalo, Buffalo, NY, USA University of Liverpool, Liverpool, UK Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA, USA CSC-IT Center for Science, Espoo, Finland Department of Geography, Pennsylvania State University, University Park, PA, USA Department of Physical Geography, Utrecht University, Utrecht, The Netherlands The Royal Netherlands Meteorological Institute, De Bilt, The Netherlands 14 10 2025 2025 1 45 Copyright: © 2025 Johanna Beckmann et al. 2025 This work is licensed under the Creative Commons Attribution 4.0 International License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/4.0/ This article is available from https://egusphere.copernicus.org/preprints/2025/egusphere-2025-4069/ The full text article is available as a PDF file from https://egusphere.copernicus.org/preprints/2025/egusphere-2025-4069/egusphere-2025-4069.pdf

Ocean-driven ice shelf melting is a major contributor of present and future ice loss from the Antarctic Ice Sheet. In the Ice Sheet Model Intercomparison Project (ISMIP6) Antarctic 2300 projections, sea level rise varies widely, from -0.6 to 4.4 m, highlighting significant uncertainty. Here, we assess drivers of this spread, focussing on sub-shelf melting and dynamic ice loss as well as sectors that have the potential for large-scale, rapid ice loss: the Amundsen Sea, Filchner-Ronne, and Ross sectors, and the Aurora and Wilkes Subglacial Basins. We derive two sensitivity factors for each ISMIP6 simulation: a) a melt sensitivity factor, describing how simulated sub-shelf melt rates respond to ocean thermal forcing changes; and b) a dynamic ice loss sensitivity factor, describing how simulated dynamic ice loss (and hence sea level contribution) responds to cumulative sub-shelf melt changes. Melt sensitivities range from 1.5&ndash;21.3 ma<sup>&minus;1</sup> K<sup>&minus;1</sup>, with no clear dependency on the melt parameterisation. Model simulations cluster into two groups based on calving strength. The dynamic ice loss sensitivities range from 0.1 to 2.6 (unitless), with larger variations in the Amundsen sector, and Aurora and Wilkes Subglacial Basins. These sensitivity factors are good predictors of short-term integrated melting and sea level rise, respectively, but are less robust on longer time scales. Our findings show that these factors explain much of the ensemble spread in projected ice loss to 2300. We recommend to further constrain these factors, and advocate for their use in model calibration and emulator design, with the ultimate aim of explaining uncertainties in future projections of sea level rise from Antarctica.

 Monash University Science Uplift Grant