The CSIRO has warned of drastic changes to volume of Antarctic Bottom Water, the cold dense water that drives global ocean currents, after releasing recent findings.

 

The CSIRO took detailed measurements of the bottom water and compared the findings with a similar study in the 1970s, finding as much as a 60 per cent reduction in the volume of the water.

 

The 25-day observing program measured temperature and sailinty at 77 sites between Antarctica and Fremantle and suggest that the densest waters in the world are gradually disapeeearing and being replaced by less dense water.

 

The amount of dense Antarctic Bottom Water has contracted each time we've measured it since the 1970s," said Dr Steve Rintoul, of CSIRO and the Antarctic Climate and Ecosystems CRC.

 

"There is now only about 40 per cent as much dense water present as observed in 1970."

 

The ocean profiles also show that the dense water formed around Antarctica has become less saline since 1970.

 

"It's a clear signal to us that the oceans are responding rapidly to variations in climate in polar regions. The sinking of dense water around Antarctica is part of a global pattern of ocean currents that has a strong influence on climate, so evidence that these waters are changing is important," Dr Rintoul said.

 

The research was carried out by more than 50 scientists on the Australian Antarctic Division's research and resupply vessel Aurora Australis, which sailed to Commonwealth Bay, west along the Antarctic coast, and returned into Fremantle.