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CSIRO Marine and Atmospheric Research
Past Seminars

Seminar Abstract

Development of a numerical model to study the seasonal circulation in Bass Strait

The three-dimensional ocean model COHERENS, a coupled hydrodynamic-ecological model, has been developed to study seasonal patterns of circulation and water mass modification in Bass Strait. This is achieved by extending model boundaries away from the region of interest and including the effects of tides, density-driven flows and surface atmospheric forcing in the form of temporally and spatially varying monthly long-term means. Initial conditions and far-field effects are incorporated using temporal harmonics from the CSIRO Climatological Atlas of Regional Seas. Tidal forcing is generated with data from the National Tidal Centre and used to simulate mixing, an important process affecting water mass properties and stratification in the Strait entrances. Model co-tidal charts are in good agreement with existing co-tidal charts. Climatologically averaged air-sea interaction is resolved over inter-annual time scales. Model heat-fluxes are compared to previous studies and existing heat flux climatologies. The ability of the model to predict water mass variation in response to atmospheric forcing and boundary forcing is assessed by comparison with atlas data, hydrographic surveys and previous studies. Parameters affecting the stratification and the heat-salt cycle are tuned using a three-dimensional box model of an area within the Strait extracted from the regional model using the same atmospheric forcing and initial conditions at the location of the box. Using an Eulerian multi-tracer method and Lagrangian particle tracking, mean wind-driven throughflow is suggested to dominate tidal action in expression of external water mass into the Strait interior. The multi-tracer transport scheme is used to reveal an area of relatively long flushing times located within the Strait interior, which exhibits seasonal spatial variation. This lends additional support to the results of a previous study and provides motivation for field evidence to be obtained to support this hypothesis.

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CSIRO = Marine Laboratories Auditorium, Castray Esplanade, Hobart

For further information, or to schedule a seminar, contact:
Karen Wild-Allen, (Oceanographic seminars) CSIRO Marine and Atmospheric Research (03) 6232 5010
Piers Dunstan, (Biological seminars) CSIRO Marine Research (03) 6232 5382
Kerrie Bidwell, Antarctic Climate and Ecosystems CRC (03) 6226 2265 & IASOS, University of Tasmania (03) 6226 2509