Currents of the continental shelf and upper slope of Tasmania

Abstract

Satellite-tracked drifters, satellite imagery, a research vessel and moorings in the waters of Tasmania, excluding Bass Strait, revealed a southward Current, sometimes called the Zeehan Current, on the outer continental shelf of western Tasmania. The current has a peak speed in winter, when it reaches around southern Tasmania as far north as Schouten Island before veering southeastward under the influence of the East Australian Current. In summer, the Zeehan Current is weaker, while the East Australian Current is stronger and overshoots southward past Tasmania by about 200 km, entraining the Zeehan Current in the process. Off western Tasmania, well seaward of the Zeehan Current, the residence time for satellite-tracked drifters was as much as one year. More than 200 km south of Tasmania in summer there was weak flow to the west. Eleven of 13 satellite drifters released in Tasmanian waters eventually meandered eastward towards New Zealand, with a travel time of over 18 months from the time of release.