The Shelf Circulation Of The Bellingshausen Sea

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.Plain Language Summary Over the past decades large changes in the volume of the West Antarctic Ice Sheet have been observed. This has been attributed to a warm water mass, the Circumpolar Deep Water (CDW). This water has been observed along the West Antarctic Peninsula (WAP) and in the Amundsen Sea. The Bellingshausen Sea, located between the WAP and the Amundsen Sea, has exhibited similar rates of ice shelf thinning, yet remains remarkably under-studied compared to regions to the east and west. We present observations of the Bellingshausen Sea from early 2019. A combination of temperature and velocity data are used to show that submarine troughs provide pathways for the warm water from offshore to reach the ice sheets. This takes place at the deepest part of the Belgica Trough and along the eastern side of the Latady trough with a recirculation of this now slightly cooler water between the two troughs. The water originating from the ice sheets leaves the Bellingshausen Sea along the western side of the Belgica Trough before flowing west toward the Amundsen Sea. Our results show that this region is a critical part of the West Antarctic circulation system, linking the WAP and the Amundsen Sea.