Overflow dynamics and bottom water formation in the western Ross Sea: Influence of tides

Abstract

The tidal impact on overflow dynamics and bottom water production in the western Ross Sea is studied with the Finite Element Ocean Model, which allows embedding a mesh with 0.5 km resolution in a coarse resolution (30 km) setup without nesting. The simulated overflow properties inside and downstream of the western Ross Sea are described. The overflow exhibits pronounced variability at both daily and spring‐neap tidal time scales in the western Ross Sea. Tides increase mixing over both the outer shelf and upper slope there. Plume jets are shaped by tidal currents at a bathymetric bend west of the Drygalski Trough mouth, descending rapidly and supplying the bottom water. A fraction of shelf water remains over the shelf and propagates westward from the Ross Sea, but it does not contribute significantly to bottom water formation because of energetic mixing over the upper slope. Compared to a simulation without tidal forcing, tides (with the major K1 and O1 constituents) increase the outflow rate over the continental slope off Cape Adare by about 70%. A set of sensitivity experiments show that the rate of bottom water production is not a monotonic function of the tidal currents amplitude. Tidal forcing with intermediate strength leads to the most efficient bottom water formation.