Climate Research Goes Nuclear In Indian Ocean

The Indian Ocean Climate Initiative project (IOCI) will use three listening devices to be installed by the Vienna-based Comprehensive Nuclear Test Ban Treaty Organisation as part of its global network for discouraging clandestine nuclear testing.

One of the monitoring posts will be installed in deep water off Cape Leeuwin in Western Australia. Others will be located off British Indian Ocean Territory in the northern Indian Ocean, and near the French sub-Antarctic island of Crozet.

The IOCI climate project will use the nuclear detection system to measure the speed at which sound signals pass through the ocean - the speed relates directly to the water temperature, increasing as the temperature rises. At this stage, the preferred site for the sound source for the IOCI project is the Cocos Islands.

The resultant data will be invaluable for measuring climate change and global warming.

CSIRO Marine Research recently won a contract for site survey work for the Cape Leeuwin hydroacoustic station, work being undertaken in conjunction with Curtin University's Centre of Marine Science and Technology, and WA-based Fugro Survey Pty Ltd.

During the past six days (June 3-9) the team was aboard the French research vessel Marion Dufresne deploying current meters and hydrophones at depths of 1600 and 150 metres off Cape Leeuwin. The Marion Dufresne returned to Fremantle Tuesday afternoon, June 9.

The CSIRO's Dr Andrew Forbes said the meters will be in the water for four months, and will provide information on deep water currents and the range of background noise (shipping, distant storm fronts, wind and waves, whales and dolphins etc.) which can be expected from acoustic listening devices deployed in the vicinity.

Dr Forbes said the IOCI project will generate information beyond the realm of established oceanographic research techniques such as satellite remote sensing and information from research ships.

"In particular it will provide a better understanding of regional influences on Australian rainfall which has strong links to Indian Ocean temperatures.

"The hydroacoustic network of sound transmitters and listening posts across the Indian Ocean will provide us with an acoustic thermometer for mapping temperatures across thousands of kilometres," Dr Forbes said.

The Indian Ocean project follows the success of similar acoustic trials in the Pacific Ocean in 1996 and 1997 by United States and Australian oceanographers. Like the Pacific trials it will use low level, low frequency sound emissions at depths of one kilometre or more, designed not to disturb dolphins and whales.

The innovative US$35 million Pacific project was delayed for more than a year while concerns over the possible impact of signals on marine mammals were laid to rest. Granted a permit in 1995 by the US National Marine Fisheries Service, the Acoustic Thermometry of Ocean Climate (ATOC) program began transmissions across the Pacific Ocean from Pioneer Seamount off San Francisco in December that year.

Now, a second transmitter has been installed off Hawaii, which also is being used to assess the effects, if any, on marine mammals, particularly humpback whales. Monitoring of marine mammals to date has established that there are no detectable effects on their behaviour due to the acoustic thermometry signals.

Dr Forbes was ATOC Director from 1994-95, while on secondment to Scripps Institution of Oceanography. He worked alongside Professor Walter Munk, the renowned oceanographer who conceived the idea of transmitting sound to detect ocean climate change.

More information from: Dr Andrew Forbes, CSIRO Marine Research, andrew.forbes@marine.csiro.au