End-of-Twenty-First-Century Changes on the Antarctic Continental Shelf under Mid- and High-Range Emissions Scenarios

Abstract Dense shelf water (DSW) formation on the Antarctic shelf plays a crucial role in our global climate system. However, possible end-of-twenty-first-century changes to ocean circulation and temperature under different climate scenarios are poorly constrained. Here, we force a 0.1° global ocean–sea ice model with spatially variable anomalies derived from a multimodel mean of 22 CMIP6 models to investigate the impact of mid-[shared socioeconomic pathway (SSP) 2-4.5] and high-range (SSP5-8.5) emissions on Antarctic margin circulation at the end of this century. We perform these simulations with and without future freshwater contributions from the Antarctic Ice Sheet to assess the changes in the presence and absence of meltwater. In the experiments without anomalous meltwater, the Antarctic continental shelf warms and freshens, becoming increasingly stratified with reduced sea ice extent across all months. Reduced sea ice growth leads to freshening over the continental shelf, which drives an acceleration of the upper-ocean Antarctic Slope Current (ASC), even in the absence of future meltwater contributions. Incorporating future projections of meltwater significantly amplifies these responses, with a complete shutdown of DSW formation and export under both mid- and high-range scenarios. However, even under a midrange emissions scenario without additional meltwater forcing, substantial changes in Antarctic continental shelf circulation and hydrography are anticipated by the end of this century, including a 35% reduction in DSW formation. Our results further suggest that the temperature response around the Antarctic margins is sensitive to the magnitude of future freshwater forcing, highlighting a need for better constraints on projections of meltwater contributions from the Antarctic Ice Sheet under different climate scenarios.