EGUsphere EGUsphere EGUsphere EGUsphere Copernicus Publications Göttingen, Germany 10.5194/egusphere-2025-3166 The influence of ocean waves on Antarctic sea-ice albedo and seasonal melting, and physical-biological feedbacks Massom Robert https://orcid.org/0000-0003-1533-5084 1 2 3 Reid Phillip 4 2 Warren Stephen 5 Light Bonnie https://orcid.org/0000-0003-2640-5738 6 Perovich Donald https://orcid.org/0000-0002-0576-0864 7 Bennetts Luke https://orcid.org/0000-0001-9386-7882 8 15 Uotila Petteri https://orcid.org/0000-0002-2939-7561 9 O'Farrell Siobhan 10 Meylan Michael 11 Meiners Klaus 1 2 3 Wongpan Pat 12 2 Fraser Alexander https://orcid.org/0000-0003-1924-0015 12 2 Toffoli Alessandro 13 Passerotti Giulio 14 Strutton Peter https://orcid.org/0000-0002-2395-9471 12 3 Chua Sean 1 2 Fedrigo Melissa https://orcid.org/0000-0002-6883-0647 1 Australian Antarctic Division, Department of Climate Change, Energy, the Environment and Water, Kingston, Tasmania 7050, Australia Australian Antarctic Program Partnership, Institute for Marine and Antarctic Studies, Battery Point, Tasmania 7004, Australia ARC Australian Centre for Excellence in Antarctic Science, Institute for Marine and Antarctic Studies, Battery Point, Tasmania 7004, Australia Australian Bureau of Meteorology, Hobart, Tasmania 7000, Australia Department of Atmospheric and Climate Sciences, University of Washington, Seattle, Washington 98195, USA Polar Science Center and Department of Atmospheric and Climate Sciences, University of Washington, Seattle, Washington 98195, USA Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire 03755, USA School of Mathematics and Statistics, University of Melbourne, Parkville, Victoria 3010, Australia. Formerly: School of Computer and Mathematical Sciences, University of Adelaide, Adelaide, South Australia 5005, Australia Institute for Atmospheric and Earth System Research/Physics, Faculty of Science, University of Helsinki, 00170 Helsinki, Finland CSIRO Environment, Aspendale, Victoria 3195, Australia School of Information and Physical Sciences, University of Newcastle, Callaghan, New South Wales 2308, Australia Institute for Marine and Antarctic Studies, Battery Point, Tasmania 7004, Australia Department of Infrastructure Engineering, University of Melbourne, Parkville, Victoria 3010, Australia School of Computing and Information Systems, University of Melbourne, Parkville, Victoria 3010, Australia Formerly: School of Computer and Mathematical Sciences, University of Adelaide, Adelaide, South Australia 5005, Australia 22 07 2025 2025 1 44 Copyright: © 2025 Robert Massom 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-2025-3166/ The full text article is available as a PDF file from https://egusphere.copernicus.org/preprints/2025/egusphere-2025-3166/egusphere-2025-3166.pdf

Identifying the processes that drive the rapid climatological retreat phase of Antarctica&rsquo;s annual sea-ice cycle is crucial to understanding, modelling and attributing observed trends and recent high variability in sea-ice extent, and to projecting future sea-ice conditions and impacts accurately. To date, the rapid annual retreat of Antarctic sea ice each spring&ndash;summer has been largely attributed to lateral and basal melting of ice floes, enhanced by wave-induced breakup of large floes. Here, based on observations and modelling, we propose that waves play important additional roles in generating previously-neglected surface and interior melting, by removing snow from small floes, flooding them, and pulverising them into slush. Results here show a resultant estimated reduction in albedo by 0.38&ndash;0.54, that increases melting by 0.9&ndash;5.2 cm day<sup>-1</sup> at 60&ndash;70<sup>o </sup>S compared to a snow-covered floe of first-year ice, and depending on surface type, wave-flooding coverage, latitude and ice density. Rapid proliferation of algae within and on the high-light and high-nutrient environment of the wave-modified ice reduces the albedo by a further 0.1 to increase the melt-rate enhancement to 1.1&ndash;6.1 cm day<sup>-1</sup>. Melting is further accelerated by a wave-induced ice&ndash;albedo feedback mechanism, similar to that associated with Arctic melt ponds but involving seawater rather than freshwater. This positive feedback is strengthened by ice-algal greening. Floe thinning and weakening by wave-melting initiate additional dynamic&ndash;thermodynamic feedbacks by increasing the likelihood of both wave-flooding and flexural breakup, leading to further floe melting. Wave melting and the associated physical&ndash;biological feedbacks will likely increase in importance in a predicted stormier and warmer Southern Ocean, and will also become more prevalent in a changing Arctic. There are implications for global weather and climate, the health of the ocean and its ecosystems, fisheries, ice-shelf stability and sea-level rise, atmospheric and oceanic biogeochemistry, and human activities.