Effect of salinity on density in the Leeuwin Current System

Abstract

Climatological temperature and salinity fields are used to calculate the salinity contribution to density and dynamic height fields in the Leeuwin Current System( LCS). While the temperature gradient is primarily linear, with warmest water to the north, the salinity fields are spatially inhomogeneous. A comparison of density fields, calculated with constant and variable salinity, shows that, off Western Australia, the density field is primarily determined by temperature. Off southwestern Australia, the density field is dependent on warm and salty (subtropical) and fresh and cold (sub-Antarctic) water masses. While the dynamic height fields, calculated with constant and variable salinity, show similar flow patterns off Western Australia, different flow patterns are found off southwestern Australia. In addition to the analysis of climatological fields,a primitive equation ocean model is used in a process-oriented study to investigate the role of salinity in the formation of currents and eddies in the LCS. Two identical ocean models, one with a climatological salinity field and the other with no horizontal salinity gradients, are run and compared with each other. Despite the model runs being initialized with similar temperature distributions there are relatively large temperature and density differences in the southwestern Australian region due to the advection of water masses by the Leeuwin Current. On the basis of the climatological analyses and the results of the model experiments, it is concluded that, descriptively and dynamically, both temperature and salinity are essential to accurately characterize the large-scale circulation of the LCS.