The Zeehan Current
Throughout the year there is a current that runs southeastward along the continental shelf edge of western Bass Strait and western Tasmania. It is called the
Zeehan Current
(ZC). Its maximum speed is about 1 knot. It is strongest in winter, weakest in summer.
In winter the ZC rounds southern Tasmania and proceeds as far north as Schouten Island, where it is entrained and carried away to the southeast by the remnants of the
East Australian Current
(EAC).
In summer the ZC only reaches the southern end of Tasmania before it is wrapped into the EAC, which reaches further southward in summer (its waters can be found 200 km or more south of Tasmania).
In 1997 we used the research vessel
Franklin
to study the currents around Tasmania. The diagram shows a section across the Zeehan Current out from Strahan in December 1997. The currents were measured with an acoustic device mounted in the ships hull. Temperature and salinity (and other properties not shown) were measured with a device lowered by winch from the ship.
In the top right panel the blue colour indicates a southward component of current that reaches 0.3 m/s (0.6 knots) at the edge of the continental shelf. The salinity panel (top left) shows low salinity waters spreading out across the shelf from Macquarie Harbour. These waters are slightly warmer than the marine waters (bottom left panel).
