Abstract

The future response of ice shelves to climate through ocean warming is a key unknown for climate projections, especially global sea level rise. The Ross Ice Shelf ocean cavity is one of the least observed regions in the ocean, with its broad circulation patterns primarily inferred from remotely sensed estimates of tides, bathymetry, and melt rates. I aim to advance our understanding of the ocean cavity under the Ross Ice Shelf – the southern-most and largest-by area of all Earth’s ice shelves. To achieve this, I analyzed a multi-year hydrographic moored timeseries from the central Ross Ice Shelf cavity (80◦39.497′S, 174◦27.678′E). These data help address three key processes: (i) the general circulation; (ii) the appearance and impact of baroclinic eddy events; and (iii) tidal modulation of the ice-ocean boundary layer structure and the implications for ice melting. In terms of circulation and the inter-annual changes, stronger melting/refreezing occurred between late September 2019 to late December 2019, which is linked to the inter-annual sea ice production in the Ross Ice Shelf Polynya. Notably, cold-water interleaving in the mid-water column exhibits distinct seasonality. An analysis of baroclinic eddies identifies coherent structures that are around 22 km in diameter with a velocity scale of between 0.8 and 1.8 cm/s. The thermohaline structure of the eddies suggests that they have the potential to entrain High Salinity Shelf Water from the benthic water column to the mid-water column. On the question of tidal modulation of the ice shelf-ocean interaction, the results suggest that tides modulate the melt rate by altering the boundary layer structure over a spring-neap cycle. These new findings demonstrate the rich variability within the Ross Ice Shelf ocean cavity, ranging from large interannual-seasonal scales, through to multi-week eddy scales and then down to tidal and mixing timescales.