Voyage detects Southern Ocean change

A scientific expedition, led by Dr Steve Rintoul from the Wealth from Oceans Flagship and Antarctic Climate and Ecosystems Cooperative Research Centre, has found evidence that the deep waters of the Southern Ocean are cooler and less salty than they were 10 years ago. Platform for the eight-week marine science and oceanography expedition the Australian Antarctic Division’s research ship Aurora Australis. 

Dr Rintoul said he was surprised at the extent and speed of the changes observed. He concluded from observations that the deep ocean is a much more dynamic environment than anticipated, and closely connected to the surface layers of the Southern Ocean.

“Ocean circulation has a big influence on global climate, so it is critical that we understand why this is happening and why it is happening so quickly,” says Dr Rintoul. “We used to think of the deepest layers of the ocean as being very stable in their properties and current patterns.”

However, the results cannot be interpreted as evidence of climate change. Long-term natural cycles may have caused the observed changes.

Satellite monitoring of salinity and temperature

Nineteen free-floating ocean robots known as Argo floats were also deployed, as part of an international ocean monitoring effort. The floats measure temperature and salinity throughout the water column, between the sea surface and 2000m depth below, every 10 days. The information is relayed by satellite to scientists in Australia and around the world, providing a continuous measure of ocean change; while the drift of the floats provides information on current speeds.

“These automated systems will make a huge contribution to our understanding of remote and hostile regions like the Southern Ocean,” Dr Rintoul said.

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The Wealth from Oceans Flagship is a CSIRO initiative and part of the National Research Flagships program that aims to deliver scientific solutions to advance Australia's most important national objectives. One of the largest scientific initiatives ever mounted in Australia, it aligns closely with the Federal Government's National Research Priorities. The initiative brings together our national research resources to deliver breakthroughs in fields ranging from healthcare to light metals and the environment.