The Forcing of Low Frequency Motions within Bass Strait

Abstract

Three months of coincident sea-level and current meter data collected during the autumn of 1984 is analyzed so as to determine the relative importance of local wind stress and coastal-trapped waves (CTWs), incident from the Great Australian Bight, in driving low frequency motions within Bass Strait. The analysis is facilitated by the development of analytical models for Kelvin waves within the strait that are forced by these agents and which allow for backscattering by the adjacent shelves. Such backscattering arises from the requirement that the Kelvin wave pressure field within the strait match that of the CTWs that are generated on the adjacent shelves. Two predictions that sea-level variability vanish at the southeast strait corner and be dominated by incident CTW energy at the northwest strait corner are substantiated both directly by the data and indirectly through a fit of the forced Kelvin wave models. For the period of analysis, the data and fitted models also show that at relatively high frequencies (period 80 h), motions within the strait are predominantly driven by local wind stress. In the energy containing 240 h band, both local wind and incident CTWs are found to be of equal importance in driving the net energy flux through the eastern strait mouth.