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<p>Both theoretical and numerical modeling studies of the current system off western  and southern Australia are conducted to characterize the features of the current system,  their temporal variability, and their impact on the sound speed structure. The theoretical  study examines why boundary current separation occurs off Cape Leeuwin creating an  area of enhanced eddy generation. It is shown that the beta effect, vortex stretching, and  streamline curvature all act to decelerate the current and to thus enhance separation. The  current is then turned left under the influence of Coriolis force and subsequently forms  meanders which then detach from the current as eddies.  The model results, using the Princeton Ocean Model (POM), reproduce the main  features of the current system. They also provide insight into the generation of the main  features. In particular, the current direction is caused by the thermohaline gradient, while  topography is responsible for the location of the current along the shelf break. Current  speed results from a combination of thermohaline gradient, the opposing wind, and  topography, while meanders and eddies result from the opposition of the thermohaline  and wind forcing. The gyre and upwelling in the Great Australian Bight are caused by  the change in wind direction in summer.  Daily wind experiments are shown to capture the seasonal variability of the  current system with the Leeuwin Current along the western coast stronger in winter than  in summer and mesoscale activity highest in summer. Seasonal and interannual  variability are highlighted with the gyre and upwelling in the bight and along Kangaroo  Island appearing intermittently but always in summer. Lastly mesoscale features in the  current system, advection of water by the surface current and undercurrent, eddies, and  upwelling are all shown to cause significant changes in sound speed which can adversely  affect sonar operations.
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<br>Subjects: Ocean currents.; Leeuwin Current System; Ocean Modeling; Princeton Ocean Model; POM; eddy; mesoscale; Great Australian Bight; Australia; boundary current separation</div>
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Miller, Henry A.</div>
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