Winter thermohaline evolution along and below the Ross Ice Shelf.

The Ross Ice Shelf floats above the southern sector of the Ross Sea and creates a cavity where critical ocean-ice interactions take place. Crucial processes occurring in this cavity include the formation of Ice Shelf Water, the coldest ocean water, and the intrusion of Antarctic Surface Water, the main driver of frontal and basal melting. During the winter, a polynya forms along the Ross Ice Shelf edge, producing a precursor to Antarctic Bottom Water known as High Salinity Shelf Water. Due to the difficulty of direct exploration of the Ross Ice Shelf in the winter, processes occurring there have been only hypothesized to date. Here we show thermohaline observations collected along the Ross Ice Shelf front from 2020 to 2023 using unconventionally programmed Argo floats. These measurements provide year-round observations of water column changes in and around the Ross Ice Shelf cavity, allowing to quantify production of High Salinity Shelf Water, ocean heat content and basal melt rates.