Impacts of Antarctic Meltwater under combined greenhouse and prescribed freshwaterforcing in EC-Earth3

Meltwater from the Antarctic Ice Sheet and shelves, driven by climate change, is projected to alter Southern Ocean stratification, impacting the location and intensity of deep convection. These changes could significantly influence the characteristics and stability of large-scale ocean circulations, ultimately impacting the global climate system. However, most state-of-the-art climate models do not account for meltwater-related processes, leaving their effects under future scenarios poorly understood. 

To address this gap, we use simulations with the EC-Earth3 coupled climate model as part of the Southern Ocean Freshwater Input from Antarctica Initiative (SOFIA). In idealized preindustrial simulations, we assess the model's sensitivity to freshwater input location — considering both distance from the Antarctic coast and sector of injection —and the effects of accounting for latent heat from calving. As a total, we find increased sea ice cover, though notable decrease is found over the Weddel Sea. In correspondence of this negative sea ice anomaly we analyze changes in stratification and in Antarctic Bottom Water formation. In historical and future scenario simulations we analyze how the mechanisms leading to increased sea ice extent and changes in deep convection are modulated by global warming when more realistic prescribed freshwater forcing is combined to increasing greenhouse gas concentrations. We analyze both high and low-end emission scenarios and assess whether the nonlinearity in the forcing is mirrored in a nonlinearity of the response in the large scale ocean circulation. Our findings underscore the importance of improving the Southern Ocean warm bias to enhance the reliability of future climate projections.