It is wetter in the south

over the past 22 years, ocean warming has caused an eight per cent increase in rainfall over the Southern Ocean and the South Pacific. Annie Wong, oceanographer at the Antarctic Cooperative Research Centre ( acrc ) in Hobart, Australia, says that warmer ocean temperatures are intensifying the cycle of rainfall, introducing greater volumes of freshwater to the sub-polar regions. A research team, which included scientists from acrc , reports a systematic decrease of salinity -- or 'freshening' -- in waters deeper than 500 metres in the Indian Ocean, the Tasman Sea and the North and South Pacific. According to Wong, observations at the surface are too sparse to directly measure this effect. But confirmation of the process has been found in the deep ocean.

"This is the first evidence from deep ocean measurements of systematic increases in rainfall patterns over the polar oceans," says Wong. "The results are consistent with greenhouse warming in the Pacific and the Southern Ocean, causing an increase in rainfall of eight per cent over 22 years," adds a co-researcher.

Direct observations of rainfall and salinity over the Southern Ocean are sparse and unreliable, say the researchers, but the results are consistent with ice cores from Wilkes Land, Antarctica, which show that snow accumulation increased over a similar period by 23 per cent. The increase in Southern Ocean precipitation is about three times greater than that predicted by recent computer simulations of ocean responses to atmospheric warming for the same period, says a researcher from acrc .