Climatology of internal tides at a shelf-break location on the Australian North West Shelf

Abstract

The concept of defining an internal tide climate is used as a means of providing an assessment of the amplitude of semi-diurnal vertical displacements of density interfaces and of horizontal baroclinic currents at a particular location. The analysis uses current meter and thermistor chain observations from North Rankin, a location just seaward of the shelf break on the Australian North West Shelf, spanning a period of 28 months. Contributions from both principal lunar (M₂) and principal solar (S₂) period internal waves are considered. The final climatological averages (monthly values) show the baroclinic currents to be comparable to or stronger than the semi-diurnal barotropic currents at the same location for the majority of the year (October through to May). The temporal variability closely follows the variability in the stratification with very weak baroclinic motion during the winter months (June to September).