SYDNEY, Aug 17 (Reuters) - Australian scientists want to string a vast array of probes across the oceans of the southern hemisphere to warn of changes in ocean circulation that may affect the global climate.

The senior science adviser to the U.N.-backed World Climate Research Programme on Friday called for the establishment of a network of deep ocean moorings to extend a system already in operation in the northern hemisphere.

Instruments could be strung across the South Atlantic and through the Indonesian archipelago, as well as in the Southern Ocean where special designs would be necessary, said John Church of the government-backed Commonwealth Scientific and Industrial Research Organisation.

A North Atlantic moored network of scientific instruments already provides measurements of the northern "overturning circulation" conveyor belt of ocean currents, which forms a giant loop from the Gulf of Mexico to Iceland and back.

"The establishment of such a system in the southern hemisphere is critical to providing the additional data ocean scientists need to more accurately monitor any shifts in the global ocean circulation that influence world climate," Church said.

After a year of observation, a team of international scientists this week reported that the conveyor belt circulation system may vary widely over 12 months, but there was not yet enough data to tell whether global warming was having an impact.

Church told Reuters that the establishment of monitors in the oceans of the southern hemisphere would require international co-ordination and would cost "tens of millions" of dollars to establish.

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