Major currents of Tasmania
What affects the movement of water in the ocean? If you think of a current flowing in a river the direction of the current is effectively downhill, with gravity causing the water to flow along a path of least resistance into a lake or the ocean. Does the sea work like a river?
Spending a day by the sea you may notice some ocean currents at work, such as localised rips or larger-scale tidal movements. Currents in the ocean can be quite complicated and may be driven by wind, temperature differences, water densities or tides.
Tasmania has three major currents systems which influence its coastal waters - the East Australian Current (EAC), the Leeuwin and the Antarctic Circumpolar Current.
East Australian Current:
Responsible for the lovely warm waters along the east coast of Tasmania, the EAC moves southward from near Fraser Island in Queensland to the eastern shores of Tasmania. Remember the movie Finding Nemo? The EAC is the current that helped Marlin find his way to Sydney. The EAC is usually stronger in summer, when it reaches further south, often bringing with it northern tropical species such as tuna. There have even been large sea turtles following this current into Bass Strait!
Leeuwin and Zeehan Current:
The East Australian, Leeuwin and Antarctic circumpolar currents and their relationship to the Australian and Tasmanian coast.
Antarctic Circumpolar Current:
A third current system, the Global Conveyor Belt, originates in the southern ocean as the Antarctic Circumpolar Current. This is an ocean current created by density and temperature variations in the water, (thermohaline circulation). Thermohaline describes currents that are the result of differences in temperature (thermo) and salinity (haline). As the Antarctic water begin to freeze, very cold and salty water is left behind. The density of this water becomes quite high and it sinks below the surface (euphotic zone), deep into the ocean, and moves toward the equator. Eventually this water will warm, and as it does, it rises to the surface bringing with it nutrients from the deep.
Links and further Information:
To see what the currents are up to around Australia:
• CSIRO currents showing the latest maps http://www.cmar.csiro.au/remotesensing/oceancurrents/
A clear animation to see how the oceans move around the coast and where they originate from:
• CSIRO animation of the currents circumnavigating Australia http://www.cmar.csiro.au/currents/animations.htm
Source Information:
CSIRO website Australiasian ocean currents fact sheet: http://www.csiro.au/resources/AustralasianOceanCurrents.html
Seas at the Millennium: An Environmental Evaluation, The Tasmanian Region CH 95, Ed C.Sheppard
Hobday, A. J., E. S. Poloczanska, and R. J. Matear (eds) (2008). Implications of Climate Change for Australian Fisheries and Aquaculture: a preliminary assessment. Report to the Department of Climate Change, Canberra, Australia. August 2008.
