The scientists set out from Hobart in Tasmania on Tuesday aboard the French icebreaker l'Astrolabe, bound for the French Antarctic base of Dumont D'Urville.

During the 2,000 kilometre (1,250 mile) round trip, they will use a below-deck laboratory to conduct tests into the capacity of the ocean to absorb greenhouse emissions.

It is the first of a series of voyages by l'Astrolabe this season, with the Australian icebreaker Aurora Australis to head south from Fremantle later this year to undertake similar research.

The team leader, Commonwealth Scientific and Industrial Research Organisation (CSIRO) research scientist Bronte Tilbrook, said the Southern Ocean soaks up man-made fossil fuel carbon dioxide (CO2) and is one of the major controls on CO2 in the atmosphere.

"The oceans themselves are a bit like a sponge for fossil fuel carbon dioxide," Tilbrook said. "We know since pre-industrial times they have taken up almost half the fossil fuel CO2 emissions and will continue to do so in the future.

Tilbrook said the latest voyage was part of a long-term project to understand how the Southern Ocean absorbs CO2 and how that phenomenon might change.

"We are also sampling to try to understand the biological and physical controls on the uptake because there are indications that the uptake may change if climate changes," said Tilbrook.

"As the CO2 is taken up into the ocean, it also acidifies surface waters, creating very small changes that could affect or disrupt parts of the ecosystem.

"We are on the verge of getting a reasonable appreciation of what they might be and how severe they might be."

The French team leader, University of Paris professor Alain Poisson, said scientists needed to know more about the evolution of the oceans and atmosphere. "This area is critical because if something happens here it will react on the global climate," he said.

CSIRO, the Australian Greenhouse Office, the Australian Antarctic Division, and the Antarctic Climate and Ecosystems Cooperative Research Centre are jointly funding the Australian mission.

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