Fabio Boeira Dias: Sensitivity of Antarctic Bottom Water projections to meltwater parameterizations
Despite the importance of Antarctic Bottom Water (AABW) to the climate system, current climate models struggle to represent the complex interaction of coastal processes that govern its formation, leading to large uncertainties in projections of future AABW. Previous studies have highlighted the role of ice shelf basal melting in slowing AABW formation. However, latent heat loss associated with ice melting is often neglected and meltwater is prescribed at the surface. Here, we investigate the AABW response to increasing basal melting by injecting meltwater at depth and explicitly accounting for latent heat loss using ACCESS-OM2-01 simulations. Our results reveal strong sensitivity to these processes. Under a moderate melting scenario (pan-Antarctic anomaly of 0.015 Sv), including both deep injection and latent heat loss reduces the AABW slowdown from ~24% to 7% relative to surface injection without heat loss. In a high melting ''Antwater`` scenario (0.1 Sv), the response shifts from a complete shutdown to a ~30% reduction. Sensitivity experiments indicate that latent heat loss is the dominant mechanism: simulations with identical latent heat loss but different meltwater input (deep versus surface) produce nearly identical AABW response. Latent heat loss offsets shelf freshening by promoting sea-ice formation and brine rejection, thereby limiting freshening of source waters and reducing the AABW slowdown. These results underscore the importance of accurately representing basal melting processes in climate projections.