EGUsphere EGUsphere EGUsphere EGUsphere Copernicus Publications Göttingen, Germany 10.5194/egusphere-2025-1990 The Influence of Glacial Northern Hemisphere Ice Sheets On Atmospheric Circulation Saini Himadri 1 2 3 Hutchinson David K. https://orcid.org/0000-0001-9385-4782 1 2 Brown Josephine R. 3 4 Drysdale Russell N. https://orcid.org/0000-0001-7867-031X 3 Du Yanxuan https://orcid.org/0009-0004-7246-4450 3 4 Menviel Laurie https://orcid.org/0000-0002-5068-1591 1 2 Climate Change Research Centre, University of New South Wales, Sydney, New South Wales, Australia The Australian Centre for Excellence in Antarctic Science, University of Tasmania, Hobart, Tasmania 7001, Australia School of Geography, Earth and Atmospheric Sciences, University of Melbourne, Melbourne, Victoria, Australia Australian Research Council Centre of Excellence for Weather of the 21st Century, University of Melbourne, Melbourne, Victoria, Australia 15 05 2025 2025 1 27 Copyright: © 2025 Himadri Saini 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-2025-1990/ The full text article is available as a PDF file from https://egusphere.copernicus.org/preprints/2025/egusphere-2025-1990/egusphere-2025-1990.pdf

During the last glacial period, Northern Hemisphere (NH) ice sheets significantly influenced atmospheric circulation, yet their broader impacts beyond the North Atlantic remain underexplored. Using the Australian Earth System Model (ACCESS-ESM1.5), we simulate a glacial climate around 49,000 years ago (49 ka) during Marine Isotope Stage 3 (MIS 3, 65–25 ka), a period marked by prominent millennial-scale variability. Our findings demonstrate that the NH ice sheets induced a southward shift of the NH westerlies, increasing rainfall over Eurasia during boreal summer while reducing it in winter. The ice sheets' influence also extended across the tropics and the Southern Hemisphere (SH), driving a southward displacement of the Intertropical Convergence Zone (ITCZ) and the NH Hadley cell during austral summer, intensifying Australian rainfall. Additionally, including the Laurentide and Antarctic ice sheets (LIS and AIS) shifts the SH Hadley cell and the SH westerlies equatorward during JJA. These findings highlight the non-linear interactions between ice sheets, large-scale atmospheric circulation, and precipitation patterns.