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New measurements by oceanographers of two significant deep ocean currents which meet off North West Australia will have a major impact on scientists' understanding of Australia's climate and the ocean influences around Australia.
The scientists, from CSIRO Oceanography, set out during a research cruise last month to build their profile of the Indonesian Throughflow, a current flowing from the Pacific to the Indian Ocean and considered a vital link with a role in driving the world's climate system.
New data taken during the cruise will be analysed over the next 12 months. They will shed more light on the amount of heat being transported by the oceans and contribute to improving long-term prediction of rainfall over Australia.
During the voyage, scientists also found that the major regional, current, the South Equatorial Current. Is stronger and deeper than previously thought, carrying 50 million cubic metres of water per second or an equivalent flow of about 250 Amazon Rivers.
The South Equatorial Current is a strong westward flow spanning the entire width of the Indian Ocean and which is fed by waters from the northern and southern Indian oceans, as well as water from the Pacific Ocean via the Indonesian Throughflow.
Temperature and salinity measurement of the Indonesian Throughflow and the South Equatorial Current were being made as part of the World Ocean Circulation Experiment (WOCE).
The Indonesian Throughflow is of particular importance to Australia, transporting large amounts of warm water from the Pacific into the Indian Ocean. This in turn warms the sea surface of the Indian Ocean and increases rainfall over Western Australia.
On board the CSIRO Oceanography research vessel "RV Franklin', Chief Scientist Dr Susan Wijffels said that measuring the Throughflow accurately is important. "Our computer climate models must take the influence of the Throughflow into account if we are going to simulate the weather over the Indian and Pacific Oceans."
"Testing these models against today's climate is vital if we are going to be able to predict accurately the climate in an enhanced greenhouse world, " she said.
Dr Wijffels said that while oceanographers have known of the South Equatorial Current and its influence on climate from Western Australia to Africa, little was known about its vertical profile and makeup.
"The new measurements in the Current indicate that it is far stronger and deeper than we had previously thought. At the surface we found currents of about 2 knots in the core of the flow, while the flow penetrates to about a kilometre in depth. From a similar cruise in April of this year, we also know that the currents change greatly from season to season, even at depth."
"The cruise has given us more vital information that will underpin our efforts to assess both climate variability and climate change."
The World Ocean Circulation Experiment began about 10 years ago and is the largest scientific survey of the global ocean ever attempted, involving scientists from more than 40 countries and using satellites, drifters and research ships simultaneously to obtain an accurate picture of the ocean's physical properties.
Dr Wijffels said sampling on the latest cruise began off Shark Bay in Western Australia and extended northward to the Indian Exclusive Economic Zone near Christmas Island, completing another component of Australia's contribution to WOCE.
For further information please contact:
Susan Wijffels
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