Huneke, Wilma G.C.Hogg, Andrew Mc C.Dix, MartinBi, DaohuaSullivan, ArnoldMcGregor, ShayneHolgate, Chiara M.O’Farrell, Siobhan P.Oliveira, Micael J.T.2026-02-112026-02-111991-959XORCID:/0000-0002-3645-2856/work/205113898ORCID:/0000-0001-5898-7635/work/205113939ORCID:/0000-0001-8624-365X/work/205115211https://hdl.handle.net/1885/733805421A new configuration of the Australian Community Climate and Earth System Simulator coupled model, ACCESS-CM2, with a higher resolution ocean-sea ice component at 0.25° is introduced. The higher resolution ACCESS-CM2-025 model was developed to better represent the ocean mesoscale and expand the scope of climate modelling research applications. The individual model components have not been changed compared with ACCESS-CM2-1, the existing lower resolution version of the model at 1°, which was one of Australia’s contributions to the World Climate Research Program’s Coupled Model Intercomparison Project Phase 6 (CMIP6). This paper assesses the simulated climate for a 500 years present-day run in ACCESS-CM2-025 against observations, the lower resolution ACCESSCM2-1 model, and two ocean-sea ice models using the same model components and comparable grid resolutions but with prescribed atmospheric forcing. ACCESS-CM2-025 is more energetic and performs better in regions of elevated ocean mesoscale variability such as at western boundary currents. The higher resolution ACCESS-CM2-025 also features a more realistic ENSO life cycle and seasonality, with a reduced biennality, which is common in the lower resolution ACCESS-CM2-1. Both ACCESS-CM2 models share many biases, particularly near the sea surface and also affecting sea ice coverage, reflecting insufficiency in the atmospheric model component. While ACCESS-CM2-025 exhibits improved time-mean deep convection, sea ice, and mixed layer depth in the North Atlantic, it also experiences multidecadal variability, which is evident in many variables, including the Atlantic Meridional Overturning Circulation.WH is supported by the Australian Research Council Centre of Excellence for Climate Extremes (CE170100023). AH, SM and CH are supported by the Australian Research Council Centre of Excellence for the Weather of the 21st Century (CE230100012). This research was undertaken on the National Computational Infrastructure (NCI) in Canberra, Australia, which is supported by the Australian Commonwealth Government. This research used the ACCESS-NRI's model ACCESS-CM2 infrastructure, which is enabled by the Australian Government's National Collaborative Research Infrastructure Strategy (NCRIS). We thank the COSIMA consortium ( http://cosima.org.au , last access: 31 January 2025) for technical support and the development of the ACCESS-OM2 model configurations used. Part of ACCESS modelling work was jointly funded through CSIRO and the Earth Systems and Climate Change Hub and subsequent Climate Systems Hub of the Australian Government's National Environmental Science Program (NESP2). ACCESS simulations, data processing and data publication were undertaken with the assistance of resources from NCI Australia, a NCRIS-enabled (National Collaborative Research Infrastructure Strategy) capability supported by the Australian Government. We thank the editor, Riccardo Farneti, and three reviewers (Brandon Reichl, Mitchell Bushuk, and one anonymous reviewer) for their insightful comments that improved the manuscript. WH is supported by the Australian Research Council Centre of Excellence for Climate Extremes (CE170100023). AH, SM and CH are supported by the Australian Research Council Centre of Excellence for the Weather of the 21st Century (CE230100012). This research was undertaken on the National Computational Infrastructure (NCI) in Canberra, Australia, which is supported by the Australian Commonwealth Government. This research used the ACCESS-NRI’s model ACCESS-CM2 infrastructure, which is enabled by the Australian Government’s National Collaborative Research Infrastructure Strategy (NCRIS). We thank the COSIMA consortium (http://cosima.org.au, last access: 31 January 2025) for technical support and the development of the ACCESS-OM2 model configurations used. Part of ACCESS modelling work was jointly funded through CSIRO and the Earth Systems and Climate Change Hub and subsequent Climate Systems Hub of the Australian Government’s National Environmental Science Program (NESP2). ACCESS simulations, data processing and data publication were undertaken with the assistance of resources from NCI Australia, a NCRIS-enabled (National Collaborative Research Infrastructure Strategy) capability supported by the Australian Government. We thank the editor, Riccardo Farneti, and three reviewers (Brandon Reichl, Mitchell Bushuk, and one anonymous reviewer) for their insightful comments that improved the manuscript. This research has been supported by the Australian Research Council (grant nos. CE170100023 and CE230100012). This research has been supported by the Australian Research Council (grant nos. CE170100023 and CE230100012).25en© 2025 The Authors2025-12-1510.5194/gmd-18-9991-2025105024781840