The circulation of the Bellingshausen Sea: heat and meltwater transports

Over past decades, the West Antarctic Ice Sheet has experienced rapid thinning of floating ice shelves as well as retreating grounding lines across most of its marine-terminating glaciers. The transport of warm Circumpolar Deep Water (CDW) on to the continental shelf, extensively documented in the West Antarctic Peninsula (WAP) and the Amundsen Sea, has been identified as the key process for inducing these changes. The Bellingshausen Sea sits between the WAP and the Amundsen Sea and has exhibited similar or even higher rates of ice shelf thinning, yet it remains remarkably understudied compared to regions to the east and west. We propose that the Bellingshausen Sea plays a critical role in connecting circulation features between the WAP and the Amundsen Sea and contributes to setting water properties that circulate under floating ice shelves throughout the entire West Antarctic continental shelf.

Here we present observations collected from a hydrographic survey of the Bellingshausen Sea continental shelf completed in early 2019. Using a combination of CTD, lowered and shipboard ADCP observations, as well as measurements from ocean gliders, we show that submarine troughs provide topographically-steered pathways for CDW from the shelf break towards deep embayments and ultimately under floating ice shelves in the Bellingshausen. Warm, modified CDW enters the shelf at the deepest part of the Belgica Trough flowing onshore along the eastern side of the trough. Modification of these poleward-flowing waters can be detected from meltwater concentrations exiting along the eastern side of the Belgica Trough. We track the signature of this meltwater to the western edge of the Bellingshausen Sea and will discuss the potential for the complex boundary currents system observed over the continental slope to transport water mass properties to the Amundsen Sea.