Oceanographers are calling for a multi-million dollar program to install nine hundred sophisticated deep-diving floats in the remote ocean south of Australia, says CSIRO's Steve Rintoul.

"We know that the Southern Ocean influences climate around the globe, and particularly rainfall in the southern states of Australia," says Dr Rintoul. "The influences are profound, but we need sustained observation to understand Southern Ocean currents and temperatures.

"Ships avoid the remote and hostile region, and as a result few measurements have been made there. Recent international experiments have started to change this situation," says Dr Rintoul.

"Measurements made by Australia and other nations over the last decade have led to remarkable advances in our understanding of Southern Ocean currents. We now have a much better appreciation of how the Southern Ocean controls regional and global climate."

New technologies such as autonomous profiling floats make it feasible to monitor the Southern Ocean for the first time, says Dr Rintoul.

Chart: Hundreds of floating 'eyes' will soon be observing changes in the Southern Ocean, if an international research proposal gets the go-ahead. Copyright CSIRO Australia, 2000

The floats do not remain on the surface, but sink to depths up to 2,000 metres gathering key ocean data before returning to the surface every 10 days to transmit their information to researchers via satellite.

Routine measurements are at present limited to a few locations where Antarctic supply vessels cross the Southern Ocean, and to remote observations by satellite. These measurements are not sufficient to examine links between ocean currents and climate.

Transects carried out by research and Antarctic supply ships, and moored sensors at key locations, are also needed.

Dr Rintoul leads the Southern Ocean research team at CSIRO Marine Research and the Antarctic Cooperative Research Centre. He and a team of international researchers made the submission to a recent conference in Europe of the Framework Convention on Climate Change (FCCC) called to design a global 'Ocean Observing System for Climate'.

Because of the sheer size of the Southern Ocean, and resource and seasonal limits to ocean monitoring, it is essential to identify key processes and locations that need to be monitored.

"As a result of recent experiments, we now know what we need to measure, and how to do it," says Dr Rintoul. "The next challenge is to find the resources required."

Dr Rintoul says Southern Ocean scientists and climatologists need to know more about ocean circulation, in particular the world's largest ocean current, the Antarctic Circumpolar Current. Patches of warm and cold water carried around Antarctica by the Circumpolar Current, a phenomenon known as the Antarctic Circumpolar Wave, have been shown to influence Australian rainfall.

"Recent discoveries like the Antarctic Circumpolar Wave are exciting because they may provide an opportunity to make longer-term predictions of Australian rainfall. To exploit this potential predictability, we need more ocean measurements," says Dr Rintoul.

Dr Rintoul points out that the isolation of the Southern Ocean poses another type of challenge for long-term ocean monitoring. While the global influence of Southern Ocean currents is now clear, the region is remote from the population centers of the northern hemisphere. This makes it more difficult to find support for an international effort to monitor the Southern Ocean.

The most recent analysis of the Antarctic Circumpolar Wave will be presented at the Australia-New Zealand Climate Forum, in Hobart from April 9-12 by Dr Peter Baines, from CSIRO Atmospheric Research.

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