Historical and Future Projected Warming of Antarctic Shelf Bottom Water in CMIP6 Models

Understanding warming on the Antarctic shelf is critical for projecting changes in Antarctic ice shelves and ice sheets. Here we assess Antarctic Shelf Bottom Water (ASBW) temperature mean-state and trends in CMIP6 models. While CMIP6 models do not resolve ice shelves, future shelf water warming will impact ice shelf vulnerability. The CMIP6 multi-model mean zonal temperature structure and mean-state ASBW spatial pattern resemble observations, although there is considerable spread across the models and a multi-model mean warm bias. The multi-model mean projects an average ASBW warming of 0.36°C (interdecile range 0.07°C–0.60°C) under SSP245 and 0.62°C (interdecile range 0.16°C–0.95°C) under SSP585 by 2100, emphasizing the influence future emissions have on shelf water warming around Antarctica. Changes in the transport of Circumpolar Deep Water onto the shelf associated with changes in the Southern Annular Mode, as well as Circumpolar Deep Water warming, are predicted to conspire to warm ASBW in the future.