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The stability of the West Antarctic Ice Sheet (WAIS) depends on ocean heat transport toward its base and remains a source of uncertainty in sea level rise prediction. The Antarctic Slope Current (ASC), a major boundary current of the ocean's global circulation, serves as a dynamic gateway for heat transport toward Antarctica. Here, we use observations collected from the Bellingshausen Sea to propose a mechanistic explanation for the initiation of the westward-flowing ASC. Waters modified throughout the Bellingshausen Sea by ocean-sea-ice and ocean-ice-shelf interactions are exported to the continental slope in a narrow, topographically steered western boundary current. This focused outflow produces a localized front at the shelf break that supports the emerging ASC. This mechanism emphasizes the importance of buoyancy forcing, integrated over the continental shelf, as opposed to local wind forcing, in the generation mechanism and suggests the potential for remote control of melt rates of WAIS' largest ice shelves. 

Antarctic Bottom Water (AABW), which fills the global ocean abyss, is derived from dense water that forms in several distinct Antarctic shelf regions. Previous modeling studies have reached conflicting conclusions regarding export pathways of AABW across the Southern Ocean and the degree to which AABW originating from distinct source regions are blended during their export. This study addresses these questions using passive tracer deployments in a 61‐year global high‐resolution (0.1°) ocean/sea‐ice simulation. Two distinct export “conduits” are identified: Weddell Sea‐ and Prydz Bay‐sourced AABW are blended together and exported mainly to the Atlantic and Indian Oceans, while Ross Sea‐ and Adelie Land‐sourced AABW are exported mainly to the Pacific Ocean. Northward transport of each tracer occurs almost exclusively (>90%) within a single conduit. These findings imply that regional changes in AABW production may impact the three‐dimensional structure of the global overturning circulation.

 

Over recent decades, the West Antarctic Ice Sheet has experienced rapid thinning of its floating ice shelves as well as grounding line retreat across its marine‐terminating glaciers. The transport of warm Modified Circumpolar Deep Water (MCDW) onto the continental shelf, extensively documented along the West Antarctic Peninsula (WAP), and in the Amundsen Sea, has been identified as the key process for inducing these changes. The Bellingshausen Sea sits between the Amundsen Sea and the northern part of the WAP, but its oceanic properties remain remarkably under‐studied compared to surrounding regions. Here, we present observations collected from a hydrographic survey of the Bellingshausen Sea continental shelf in austral summer 2019. Using a combination of ship‐based and glider‐based CTD and lowered ADCP observations, we show that submarine troughs provide topographically steered pathways for MCDW from the shelf break toward deep embayments and ultimately under floating ice shelves. Warm MCDW enters the continental shelf at the deepest part of the Belgica Trough and flows onshore along the eastern side of the trough. Modification of these shoreward‐flowing waters by glacial melt is estimated by calculating meltwater fractions using an optimal multiparameter analysis. Meltwater is found to be elevated at the western edge of both the Latady and Belgica troughs. Meltwater distributions, consistent with other diagnostics, suggest a recirculation in each trough with modified waters eventually flowing westward upon leaving the Belgica Trough. Our results show that the Bellingshausen Sea is a critical part of the larger West Antarctic circulation system, linking the WAP and the Amundsen Sea.