Found: Missing Link of the World's Ocean Currents
Kathy Marks in Sydney
Ken Ridgway, a scientist with the Commonwealth Science and Industrial Research Organisation (CSIRO), said yesterday that the current - called the Tasman Outflow, and found at a depth of 2,600 to 3,300ft - may play an important role in the conveyor belt's response to climate change.
The missing deep ocean pathway, known as a "supergyre", links the three ocean basins of the southern hemisphere: the Indian, Pacific and Atlantic. Research by a CSIRO team has confirmed that the waters south of Tasmania form a "choke point", connecting the main "circulation cells" in the three oceans.
Mr Ridgway said it had long been known that a system of currents north of Australia, called the Indonesian Throughflow, drains water from the Pacific into the Indian Ocean through Indonesia - a process that influences rainfall in Australia. "Now we can see that they (deep ocean pathway currents) move south of Tasmania as well, another important link (between the Pacific and Indian Oceans)," he said.
Sea water flows around anti-clockwise pathways, known as "gyres', which are the size of ocean basins. The gyres distribute nutrients from the deep ocean, generating life on the continental shelves and slopes. They also drive the circulation of the world's oceans, creating currents and eddies, and helping to balance the climate system by transferring heat from the tropics towards the polar region.
The newly discovered Tasman Outflow, which sweeps out of the Tasman Sea, is classed as a "supergyre", connecting gyres in the three oceans.
The research team analysed thousands of temperature and salinity data samples collected between 1950 and 2002 by research ships, robotic ocean monitors and satellites. They identified linkages between the gyres, and established that the supergyre transfers water to all three ocean basins.
Mr Ridgway and his fellow author, Jeff Dunn, said that identification of the supergyre would enable scientists to explain more accurately how the ocean governs global climate.