ABOARD THE AURORA AUSTRALIS, Southern Ocean, Jan 9 AAP – Far into the Southern Ocean a team of scientists and their expensive machine are working to find out if the seas will continue to do us a favour by soaking up carbon and curbing the rate of climate change.
On the icebreaker Aurora Australis between Tasmania and Antarctica, the team watch a little nervously as their Conductivity, Temperature and Depth (CTD) device is lowered over the side on a thin cable to plunge thousands of metres to the seabed.
As the half-million-dollar device is hauled back up, specially-designed flasks open at different depths to trap seawater for analysis while other instruments measure temperatures, salinity and oxygen concentrations.
The scientists hope to repeat the procedure more than 80 times on their six-week voyage from Hobart to Antarctica then on to Fremantle.
Appropriately, they’re travelling in the 100-year-old wake of Australian explorer-scientist Douglas Mawson’s 1911-14 Antarctic expedition, with the Aurora Australis due to stop at Commonwealth Bay on the ice around January 12 for centenary commemorations.
Hobart-based CSIRO oceanographer Steve Rintoul says his team is trying to see how the ocean is changing across its full depth and the only way to do that is to lower devices such as the CTD from ships.
“We don’t have a lot of measurements from across the Southern Ocean because its a pretty miserable place to work, its the waviest, windiest part of the oceans and its a long way from the shipping lanes where most vessels travel,” Dr Rintoul says.
“The Southern Ocean is particularly important for climate because it stores huge amounts of carbon dioxide and heat and by doing that it slows down the rate of climate change.
“What we are trying to discover is whether the ocean will continue to play that sort of service,” Dr Rintoul says.
The world’s oceans absorb about 25 per cent of the carbon dioxide that’s pumped into the atmosphere with the cold Southern Ocean and its unique currents absorbing about 40 per cent of that.
Dr Rintoul says the Southern Ocean is the only place where the deep part of the ocean rises up to the surface and connects with the atmosphere, either releasing carbon dioxide or picking it up.
The scientists are interested in what controls those currents, how strong they are and what controls how much heat and carbon the ocean can store, he says.
“One of the big questions in this area of science is whether the Southern Ocean will continue to absorb that much carbon dioxide as it has in the past.”
The measurements his team make to track the increase in the amount of carbon that’s dissolved in the ocean will help determine exactly how fast the Southern Ocean is absorbing carbon and whether that’s changing over time.
Dr Rintoul says his team’s work in tracking the warming of the ocean also ties in with the increasing flow-off of Antarctica’s ice into the ocean and therefore global sea level rises.
He says scientific models developed so far indicate that the land and ocean sinks that together absorb about half the carbon in the atmosphere will become less efficient as the climate changes and that will tend to accelerate climate change.
“It’s too early to tell and our work on this voyage is relevant to that.”
Dr Rintoul says the evidence is that climate change is happening and it is caused by carbon-emitting human activity.
“Our job as scientists is to provide the best scientific information we can so that society can make some decisions,” he said.
“We don’t know everything as well as we’d like. In my own view we know enough to act and we could be acting more vigorously than we are at the moment.
“It is the challenge for my generation in my view.”
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