On the dynamics of an observed thermal front off central eastern Australia

Abstract

Results from a short observational program off central eastern Australia (28.4°S) are presented. A series of events involving sharp temperature fluctuations and strong pulses in the alongshore currents are measured by a mooring array over the inner shelf. With use of AVHRR images, ADCP, and CTD surveys, it is reasoned that these events correspond to the periodic advection of a thermal front past the inshore moorings. The front involves a temperature change of 1°-2°C, with a southward jet of greater than 0.5 m s-1 over a width of 1 - 2 km in 25 m of water. The dynamical balances of the momentum equations are examined. It is demonstrated that at the onset of each event the local tendency of alongshore velocity is balanced by across-shore advection. Additionally, a quasi-balance between the surface and bottom stress terms is noted throughout the experiment demonstrating the prominence of mixing over the inner shelf.