Climate change signal detected in the In...( tures; a strong warming (about ...)

• a strong warming (about 2C over 40 years) between 40S and 50S down to a depth of 800metres;

• and, sub-surface cooling in the tropics due to deep waters rising closer to the surface.

Dr Alory says the research confirmed a long-held view that temperature changes in the Pacific and Indian oceans can be partly explained by the effect of the 'Indonesian throughflow' a system of currents which transports water between the oceans through the maze of straits and passages in the Indonesian Archipelago.

"The cooling is occurring between Australia and Indonesia where the Indonesian throughflow emerges into the Indian Ocean and is linked to the observed weakening of Pacific Ocean trade-winds," he says. The models also helped to explain trends in the subtropical Indian Ocean temperatures and changes in relevant ocean features. In this area, the deep-reaching warming is due to a strengthening of westerly winds drawing a southward shift in ocean current patterns. These findings are consistent with research in the South Atlantic and South Pacific ocean basins.

He said that the change in atmospheric conditions altering ocean temperatures weakening of Pacific Ocean trade winds and strengthening of westerly winds have been mostly attributed to human activity: the production of aerosols (tiny atmospheric particles), ozone depletion, and greenhouse gases. Strengthening westerlies are related to changes in the Southern Annular Mode an atmospheric feature similar to the El Nino Southern Oscillation and considered the dominant influence on Southern Hemisphere atmospheric variability.

Dr Alory said climate models used in the IPCC Fourth Assessment show that changes in westerly wind patterns are expected to intensify in a global warming scenario and to accentuate the southward shift in sub-tropical ocean circulation patterns.

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Contact: Dr. Gael Alory
Gael.Alory@csiro.au
61-362-325-399
CSIRO Australia
29-May-2007