Ocean robots to seek clues to climate change
22 December 2004
Robots will be released in the Southern Ocean this summer to collect vital information to help scientists detect changes in ocean properties and more accurately identify long-term climate change trends.
The 17 free-floating robots, known as Argo floats, will be released during a 10-week scientific expedition by the Aurora Australis, which leaves Fremantle tomorrow.
The floats will dive to 2000 m every 10 days, for up to five years, taking crucial temperature and salinity measurements as they ascend, as part of an international ocean monitoring programme.
The information will be relayed to scientists in Australia via the French ARGOS satellite, providing a continuous measure of ocean change; while the drift of the floats will provide information on current speeds.
The Minister for the Environment and Heritage, Senator Ian Campbell, who last week headed an Australian delegation to the United Nations Convention on Climate Change in Buenos Aires, said the Argo floats would greatly assist oceanographic research in remote and hostile regions such as the Southern Ocean
"Such research is critical to our understanding of climate change, as the ocean changes much more slowly than the atmosphere," Senator Campbell said.
"These gradual changes provide a clearer signal of long-term climate trends than the larger day-to-day oscillations in temperature."
The expedition is being led by Dr Steve Rintoul, of the Antarctic Climate and Ecosystems Cooperative Research Centre and CSIRO.
Dr Rintoul's team will conduct a range of other measurements during the voyage. These include using a probe that measures changes in salinity, temperature and oxygen levels with depth, at 30 nautical mile intervals along a transect between Fremantle and Antarctica. Any changes in these parameters could indicate a change in the Antarctic Circumpolar Current – the world’s largest current – which in turn influences climate patterns across the globe.
"While such changes will be subtle and won't make a difference to marine life in the short-term, they will provide an indication of how ocean circulation is changing," Dr Rintoul said.
Water samples will also be analysed for changes in carbon dioxide levels, providing clues to current climate trends.
"The Southern Ocean slows the rate of climate change by absorbing CO2 from the atmosphere," Dr Rintoul said.
"Models suggest that the ability of the Southern Ocean to absorb CO2 will decrease as climate changes. So we want to determine whether the ocean is still absorbing CO2 and at what rate, and if there is a limit to how much it can absorb."
An American team aboard the ship will contribute another piece of information to the puzzle by measuring turbulence in the ocean.
"A fundamental question linking oceanography and climate is where does mixing happen in the ocean," Dr Rintoul said.
"We know that dense water sinks near Antarctica and slides to the bottom of the ocean, and that somehow, warm water moves south to replace it. Somewhere the cold and warm waters must be connected, to complete the loop. We suspect it may be the Southern Ocean as it has the largest and strongest currents in the world, interacting with a very rough sea floor. We will test this hypothesis on this voyage by collecting the first direct measurements of mixing in the Southern Ocean."
The 10-week voyage is being funded through the Australian Antarctic Division, the Antarctic Climate and Ecosystems Cooperative Research Centre and the Australian Greenhouse Office.
The Aurora Australis is scheduled to sail from Fremantle at 5pm tomorrow.