Factors influencing the occurrence of Dense Shelf Water Cascades in Australia

Transport of inshore waters and suspended material off the continental shelf by Dense Shelf Water Cascades (DSWC) has important ecological and biogeochemical implications in Australian waters. Because of high rates of evaporation, denser saline water occurs in the shallow coastal regions around Australia, setting up horizontal density gradients that can drive DSWC. Ocean glider data available from the Integrated Marine Observing System (IMOS), which is operated by the Australian National Facility for Ocean Gliders (ANFOG) located at the University of Western Australia, were used to measure cross-shelf density profiles under varying wind and tide conditions for seven contrasting regions around the entire continent. Overall 97 sets of spatial and temporal resolution data from year 2008 to 2015 collected by the ocean gliders and analysed with a subset presented here. Data from 19 transects covering the years 2012 to 2015 for the Pilbara region of Western Australia, indicated that cascades occur during the autumn and winter due to cooling of the coastal waters which already have higher salinity due to evaporation during the summer months. The cross-shelf density gradient in this continental shelf was found to be maximum in July with a value of 14.23x 10(-6) kg m(-4).