Baroclinic response of Sydney shelf waters to local wind and deep ocean forcing

Abstract

A study of the forcing processes responsible for upwelling events in the coastal ocean of Sydney, Australia, has been performed using data collected over the summer of 1994 from a shore-normal-aligned mooring array and a numerical model. Analyses of the data show that vertical displacements of fluid in the nearshore zone responded principally to the local wind stress during the experimental period. However, intrusions of mesoscale East Australian Current features are shown to significantly influence the vertical structure of the water column over the middle and outer shelf regions. Numerical simulations are performed to investigate the internal processes occurring during strong steady intrusion events of the East Australian Current onto the Sydney shelf. These simulations suggest that Ekman transport in the bottom boundary layer underlying an intrusion event is not an efficient mechanism for advecting colder water into the nearshore zone on the Sydney shelf. Preconditioning of shelf waters by the East Australian Current and concurrent forcing by local winds is suggested as an efficient process by which upwelling states may be achieved in the Sydney coastal ocean.