Ocean stratification and tides control basal melting at the Ross Ice Shelf Grounding Zone.

The interactions among ice, ocean, and seafloor in Antarctic grounding zones hold major implications for global sea level rise over the coming century and beyond. Meltwater buoyancy means that grounding zone conditions influence basal boundary layer throughout the entire cavity. Because of the difficulty of direct access, grounding zone ocean environments have been sampled only a handful of times and then usually only as a brief data snapshot. Here, we present ocean data from the Kamb Ice Stream grounding zone of the Ross Ice Shelf that reveal a consistently stratified 30-meter-thick water column beneath nearly 600 meters of ice and snow. Warmer inflowing seawater is vertically separated from an overlying colder outflowing mixture of seawater and glacial meltwater. The 10-month long timeseries of stratification reveals that this layering is resilient but variable, with internal wave activity resulting in frequent mixing between the two layers that suggests a mechanistic underpinning for the grounding zone as a distinct region within the cavity.