Promotion of Dense Shelf Water formation in the Ross Sea under the future trend of the Amundsen Sea Low

Abstract. The Amundsen Sea Low (ASL) is a key low-pressure system influencing climate variability over West Antarctica. The Ross Sea is one of the major formation sites of Dense Shelf Water (DSW), precursor of the global ocean bottom water mass — Antarctic Bottom Water. This study uses CMIP6 multi-model ensemble means to project future changes in the ASL and the associated wind variations over the Ross and Amundsen Seas by the mid- and late-21st century. A high-resolution coupled ocean-sea ice-ice shelf model covering the Ross Sea and the Amundsen Sea is employed to assess how these ASL-driven future wind changes affect DSW formation in the Ross Sea. By applying ASL-induced wind perturbations to three key regions that modulate the Ross Sea DSW characteristics, the respective contributions of regional wind-driven ocean-ice coupling processes to the DSW formation are quantified. The results show that the future deepening and southward shift of the ASL will enhance sea ice production in the Ross Sea polynyas and reduce meltwater inflow from Amundsen Sea ice shelves, thereby promoting DSW formation. Relative to present conditions, ASL-related wind changes over the Ross Sea and adjacent Amundsen Sea are projected to increase DSW production by approximately 8 % by 2050 and 18 % by 2100. These findings suggest that future ASL changes could help counteract the diminishing trend of DSW in the Ross Sea and maintain the Southern Ocean meridional overturning circulation.