Model for the three-dimensional structure of wind-driven and tidal circulation in Bass Strait

Abstract

Earlier models of the circulation in Bass Strait have been extended to include vertical structure. Time- dependent circulation fields in Bass Strait, induced by wind driving at the surface and tidal oscillations along open-sea boundaries, are computed at a number of selected depths. The original two-dimensional model is combined with an analytical solution of the Ekman equations, which at each grid point provides an expression for the time-dependent flow at any depth in terms of a convolution integral over the sea- surface slope and wind stress. This model should be applicable to winter conditions when the strait is well mixed vertically and hence the dynamical effects of density stratification negligible. The predicted wind-induced circulation fields are highly depth dependent, with equilibrium surface currents in the central Bass Strait basin flowing in a direction approximately 45� to the left of the wind. At lower levels, currents are controlled by pressure gradient forces due to the sea-surface slope and friction. Significant upwelling and downwelling motions along the Victorian and Tasmanian coastlines can be inferred from these circulation fields. In the deep water off the continental shelf, currents in the upper 100 m are dominated by the (Ekman) drift current which rotates in an anticlockwise direction with increasing depth, such that the wind drift at the surface is accompanied by a measure of return flow at depth. Tidal currents are predicted in the absence of wind stress, but include the effects of bottom topography. Considerable variation with depth is found and the distinctive features are explained in terms of the relative importance of Coriolis force, bottom friction, and water depth. Comparison with the few existing observations reveals that the present model is producing realistic results.

Longshore wind, waves and currents: climate and climate projections at Ninety Mile Beach, southeastern Australia

“…Previous modelling studies indicate strong wind-tide driven currents in Eastern Bass Strait (Fandry, 1983;Sandery and Kämpf, 2007). Attempts have been made to estimate climate change impacts of sediment transport from wave energy for NMB (Charteris and Sjerp, 2009) but have been limited due to lack of available observational data and have not included the influence of the considerable wind-tide currents in this region.…”

Delineating fish-habitat associations for spatially based management: an example from the south-eastern Australian continental shelf

“…The Twofold Shelf bioregion is an exposed and currentswept area (Fandry 1983;Morrow and Jones 1988) of some 32000 km 2 that extends to about 200 m depth on the southeastern Australian continental shelf. It is the area of greatest fishing effort within one of the country's largest regional fisheries, the South East Fishery (SEF).…”

Quantifying Fish Assemblages in Large, Offshore Marine Protected Areas: An Australian Case Study

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