Role of Tides in Ice-Ocean Interactions Over the Antarctic Continental Shelf and Slope

Yidongfang (Clara) Si, University of California Los Angeles, Atmospheric and Oceanic Sciences, Los Angeles, CA, United States and Andrew Stewart, University of California Los Angeles, Atmospheric and Oceanic Sciences, Los Angeles, United States
Tides are key contributors to the circulation and water mass exchange around the Antarctic margins. Previous studies indicate that the rectification of tidal currents on the continental slopes plays a crucial role in setting the structure of the Antarctic Slope Current (ASC). Tides make large contribution to the across-shelf heat transport towards the Antarctic coast, and also affect the dense-water outflows on the continental shelf and slope. However, the interactions between tidal flows, sea ice drift and the structure and transport of the ASC remain poorly understood. In this study our primary aim is to understand how tides and wind forcing drive the ocean/sea-ice system of the ASC. We are also investigating the role of tides in modulating cross-slope exchanges.

We utilize high-resolution process modeling in idealized settings to perform a series of experiments with varying tidal amplitude, wind speed, atmospheric forcing and sea ice parameters. To better understand the dynamics of tidally-forced ice/ocean flows, we also develop a 1D model to simulate a barotropic ocean overlaid by viscous-plastic sea ice, driven by tidal forcing and wind stress. We use this 1D model to explore the effects of drag coefficients, ice rheology parameters, wind stress and tidal forcing, and quantify the stress terms at ice-ocean interface and ocean bottom. Our results show that sea ice plays a role in redistributing tidal-input along-slope momentum away from the slope current, which affects the structure of the ASC and overturning of the slope front. The rectification of tidal currents enhances the ocean-ice heat flux, modulating the upper ocean stratification, as well as the formation and export of dense shelf water. We discuss the implications of our findings for circum-Antarctic variations in the structure and overturning of the ASC, and for redistribution of water masses and sea ice around Antarctica.