Antarctic Bottom Water Sensitivity to Spatio‐Temporal Variations in Antarctic Meltwater Fluxes

Abstract

AABW formation is one of the main components of the Global Meridional Overturning Circulation (GMOC), a large-scale ocean circulation system that connects all ocean basins and controls global climate stability (Talley, 2013). Freshwater originating from the Antarctic ice sheet (AIS) enters the ice shelf cavities and marginal seas, lowering local salinities and potentially hindering the formation of Antarctic Bottom Water (AABW) (Silvano et al., 2018;Wijk & Rintoul, 2014). Thus, by changing the rate of AABW formation, AIS melting can significantly affect the state of the global climate.AABW is mainly formed at the Antarctic margins through interaction between the ocean, sea ice and ice shelves. Along the ice shelves, brine rejection and buoyancy loss in coastal polynyas forms the dense shelf water (DSW), a precursor water for AABW. DSW then flows through the continental shelf, forming AABW through further mixing with circumpolar deep water (CDW) along the continental shelf break (Carmack & Foster, 1975;Foster & Carmack, 1976). Ice melting also occurs under ice shelves, releasing freshwater and thus decreasing salinities along the Antarctic coast. Hence, increasing AIS melting can increase the buoyancy of DSW, hindering the formation of AABW (Wijk & Rintoul, 2014). Alternatively, AABW can be formed offshore by deep convection in open-ocean polynyas (e.g., Killworth, 1983), a process commonly present in models (Aguiar et al., 2017;Azaneu et al., 2013), but only observed a few times since satellites started monitoring sea ice in the Southern

Water Mass Transformations Within Antarctic Coastal Polynyas of Prydz Bay from Clustered Drifters

“…Thus, the formation of ISW and its freshening from melting and refreezing under the ice shelf can prevent the formation of AABW later on. Several studies have noted the suppressing factor of ice meltwater on Southern Ocean overturning and particularly its effect on AABW formation (Pellichero et al, 2018;Aguiar et al, 2023), which can occur in Prydz Bay after advection of shelf water under the ice shelf inducing basal melting (Liu et al, 2017;Jacobs et al, 1992). Once these sub-ice shelf waters are enriched with freshwater, they can leave the ice shelf again, mixing with surface waters or CDW to warm and form WW or mCDW.…”