Dense water formation and cross-shelf exchange on the Rottnest Continental Shelf in south-western Australia

Using temperature and salinity (and associated density) data collected using autonomous ocean gliders along the Rottnest Continental Shelf, it is shown that dense shelf water cascade (DSWC) is a process that occurs throughout the year with varying degrees of intensity. DSWC is driven by a cross- shelf density gradient due to an increase in salinity due to evaporation in summer and autumn and due to cooling in winter. In summer, due to strong wind mixing and upwelling the occurrence of DSWC is minimal. A relative increase in density in the inshore regions allows for the transport of higher density water, which may be 20 m in thickness where the water depths are 40m, to be transported offshore near the sea bed. The density currents are estimated to be ~1-2 cms-1, which is similar to those measured in other similar regions globally. The DSWC plays an important role in cross-shore exchange of the water and material.