Study of the fresh-water inflow through the eastern gate of the Ross Sea

The produc􀆟on of Antarc􀆟c Botom Water (AABW) plays a major role in determining the strength of the Meridional Overturning Circula􀆟on and, therefore, is an important element in the ocean’s contribu􀆟on to global climate. AABW is formed in few areas around the Antarc􀆟c con􀆟nent, especially in the Ross and Weddell Seas, with dis􀆟nct thermohaline characteris􀆟cs. Observa􀆟ons within the Southern Ocean’s Pacific sector indicate a decadal trend of reduced salinity of the shelf waters which are related to the AABW modifica􀆟on. Specifically in the Ross Sea, CTD data and moored observa􀆟ons are showing changes in the thermohaline characteris􀆟cs of the shelf waters, precursors of the AABW, since 1995. A freshening was observed in the western Ross Sea both at the shelf water forma􀆟on area and at the Ross Sea shelf break, where the AABW is formed and cascades to fill the Pacific Ocean deep basins. Despite the nega􀆟ve salinity trend, a rebound in salinity has been observed for the last 5 years. The Ross Sea freshening was atributed to the inflow of waters from West Antarc􀆟ca where a drama􀆟c mel􀆟ng of glaciers is occurring. To determine the freshwater inflow from West Antarc􀆟ca and the role of these waters in the salinity field variability, an oceanographic cruise was carried out during austral summer 2020 in the eastern sector of the Ross Sea. Addi􀆟onally, a sec􀆟on of the same CTD grid was repeated during January 2021. Using physical data from the CTD and LADCP casts, glider deployment and dri􀅌ers, we es􀆟mated water mass characteris􀆟cs and dynamical features. Eventually, discrete sea water sampling for chemical analyses (nutrients, carbonate system, trace metals, persistent organic compounds) has been carried out to provide new informa􀆟on about the biogeochemistry of the area and origin of the water masses.