Ocean Processes Observed in the Central Ross Ice Shelf Cavity Using a Year-Long Hydrographic Mooring

Ocean processes beneath Antarctic ice shelves have been linked to ice shelf basal melting rates, influencing Antarctic ice mass loss and global sea level change. Although ocean-driven melting accounts for a significant proportion of ice mass loss from Antarctic ice shelves, ocean processes controlling the ice shelf basal melt rates are rarely studied through direct measurements. Here, we examine processes in the central Ross Ice Shelf cavity (80°39.497'S, 174°27.678'E), the largest ice shelf in Antarctica. A hydrographic mooring was deployed for over a year, equipped with five pairs of Nortek Aquadopp current meters and Seabird SBE 37 CTD instruments. This enables examination of temporal variability from tidal through to seasonal timescales - primarily achieved here using wavelet analyses. One of the clear prior observations resolved in profile data is the temperature-salinity variability in the mid-water column. The timeseries reveals that this variability is consistent through the year. The analysis also shows subtle shifts in temperature-salinity properties around Gade lines. While there is no clear seasonal cycle identifiable this deep into the cavity, the temperature-salinity timeseries also demonstrate that meltwater has a variation in salinity of about 0.2 g/kg. This variation can be explained by sub-tidal variations resolved from the current timeseries, whereby mesoscale eddies were resolved based on point data. This suggests that westerly currents bring relatively-high salinity ice shelf water to this location, and eastly currents bring meltwater with relatively low salinity to central Ross Ice Shelf. In this study, eddy selections are also applied to the current timeseries, with the current direction being the principal selection criterion. This first analysis of long-term hydrographic data from the central Ross Ice Shelf cavity provides new insight into ocean processes that influence both East and West Antarctic ice sheets melting.