Topographic control of tides in the Ross Sea: eddy-like structures, bottom-trapped waves, and energetics

Abstract. Using a regional high-resolution coupled ocean-sea ice-ice shelf model, this study investigates tide-topography interactions, energy conversions, and tide-induced cross-slope exchange in the Ross Sea. The model resolves tidal time series and power spectral density that agree well with available mooring data. Through tidal decomposition of modelled tides, we identify a diurnal topographic mode along the Ross Sea slope, characterized by three eddy-like structures. These structures arise because the varying topography of the continental slope induces divergence and convergence in the diurnal surface‑mode tidal flows. This generates sea surface height extremes that persist longer than the time required for geostrophic adjustment, allowing rotating geostrophic flows (i.e., the topographic mode) to develop around them. The topographic mode dominates the water exchange across the slope and yields a net heat transport towards the shelf (~12 TW). The surface and topographic modes can exchange energy with each other, as indicated by alternating positive and negative patches of energy conversion rate with a magnitude reaching 1 W/m². The baroclinic tides in the Ross Sea manifest as bottom-trapped waves over the continental slope and other topographic gradients. The energy of baroclinic tides, primarily converted from the topographic mode, is an order of magnitude smaller than the barotropic tides. The barotropic component accounts for most of the tidal dissipation along the slope (~0.1 W/m²), with a minimal contribution from baroclinic tides. This study identifies tides as an important driver of heat transport onto the Antarctic shelf, which is fundamental for accurately prediction of future Antarctic ice shelf melt and global sea level rise.