Pathways of Inter‐Basin Exchange From the Bellingshausen Sea to the Amundsen Sea

• Published in: Journal of geophysical research. Oceans 2024-06, Vol.129 (6), p.n/a
• Main Authors: Flexas, M. Mar, Thompson, Andrew F., Robertson, Megan L., Speer, Kevin, Sheehan, Peter M. F., Heywood, Karen J.
• Format: Article
• Language: English
• Subjects: Antarctic ice sheet; Backscatter; Bellingshausen Sea; Circulation; Coastal currents; Continental shelves; Continental slope; Cores; Dissolved oxygen; Exchanging; Floating ice; Glaciation; Glacier melting; glider data; Hydrograph analysis; Hydrographic data; Hydrographic sections; Ice; Ice sheets; Ice shelves; ice‐ocean interactions; in situ observations; Isopycnals; Land ice; Mathematical models; Meltwater; Numerical models; Ocean temperature; Oceans; Optical properties; pathways; Remote control; Salinity; Salinity effects; seal data; Seals (animals); Thinning; Tracers; Underwater vehicles; Vertical profiles; Water masses; Water properties
• ISSN: 2169-9275; 2169-9291
• DOI: 10.1029/2023JC020080

The West Antarctic Ice Sheet is experiencing rapid thinning of its floating ice shelves, largely attributed to oceanic basal melt. Numerical models suggest that the Bellingshausen Sea has a key role in setting water properties in the Amundsen Sea and further downstream. Yet, observations confirming these pathways of volume and tracer exchange between coast and shelf break and their impact on inter‐sea exchange remain sparse. Here we analyze the circulation and distribution of glacial meltwater at the boundary between the Bellingshausen Sea and the Amundsen Sea using a combination of glider observations from January 2020 and hydrographic data from instrumented seals. Meltwater distributions over previously unmapped western regions of the continental shelf and slope reveal two distinct meltwater cores with different optical backscatter properties. At Belgica Trough, a subsurface meltwater peak is linked with hydrographic properties from Venable Ice Shelf. West of Belgica Trough, the vertical structure of meltwater concentration changes, with peak values occurring at greater depths and denser isopycnals. Hydrographic analysis suggests that the western (deep) meltwater core is supplied from the eastern part of Abbot Ice Shelf, and is exported to the shelf break via a previously‐overlooked bathymetric trough (here named Seal Trough). Hydrographic sections constructed from seal data reveal that the Antarctic Coastal Current extends west past Belgica Trough, delivering meltwater to the Amundsen Sea. Each of these circulation elements has distinct dynamical implications for the evolution of ice shelves and water masses both locally and downstream, in the Amundsen Sea and beyond. Plain Language Summary Floating ice shelves in West Antarctica are thinning, which is largely due to melting of the ice shelf base by the ocean. Here, measurements of ocean temperature, salinity, and dissolved oxygen, collected by a remotely‐controlled underwater vehicle (a glider), are used to estimate the amount of ice shelf meltwater released in the Bellingshausen Sea. Distinct cores of meltwater can be distinguished by the amount of suspended material that is present in the water, which we attribute to meltwater following different circulation pathways after entering the ocean. Historical data from seals equipped with temperature and salinity sensors provide additional information about how the meltwater circulates in the region. The seal data show the presence of a narrow coastal curr