PM - Monday, 18 February , 2008 18:38:00
Reporter: Felicity Ogilvie
MARK COLVIN: There's a new clue to what causes droughts in Australia. It comes from measurements taken in the Southern Ocean.
Data over 15 years show sea levels have risen 10 centimetres over that time.
The scientists behind the work say Australian droughts are linked to changing winds in Antarctica.
Felicity Ogilvie reports from Hobart.
FELICITY OGILVIE: While it's known as the engine room of the world's climate, not much is known about the Southern Ocean.
That's because the ocean is so rough and remote it's difficult to study.
But a French Australian team have managed to get 15 years worth of continuous data by taking measurements in the Southern Ocean from the re-supply ship that sails between Hobart and the French Antarctic base of Dumont d'Urville.
Oceanographer, Rosemary Morrow, works for the French Government.
ROSEMARY MORROW: We drop a temperature probe over the side that's connected by a wire back to our computer and it measures temperature with depth down to about one kilometre and that's the part of the ocean that changes the most in terms of temperature change. And we do that every hour, or every two hours as we leave Hobart, until we get to Dumont d'Urville.
FELICITY OGILVIE: More than 8,000 measurements have been taken and analysed.
Doctor Morrow, says the data shows there's been a sea level rise because the water has been getting warmer
ROSEMARY MORROW: It's of the order of only a few millimetres per year but over a 15 ear period, we're getting up to the order of perhaps 10 centimetre change in sea level rise. And that also doesn't seem much when you think of the tides of being one metre, but it's something that's consistently happening and in low-lying areas, that is something that can start to be dramatic.
FELICITY OGILVIE: Not only are the icy waters around Antarctica getting less icy, there's been a change in the winds.
The Programs Australian Leader, CSIRO scientist, Steve Rintoul says the changes in the Southern Ocean are affecting Australia's climate.
STEVE RINTOUL: There's increasing evidence now that winds have changed over the Southern Ocean in recent decades and those wind changes are linked to the droughts that we've had in southern Australia; both in the West and more recently in the South-East.
So, part of our work is really unravelling how the ocean and the atmosphere maybe working together to drive those changes in weather patterns.
FELICITY OGILVIE: Doctor Rintoul says the winds have pushed the Polar Current further south.
STEVE RINTOUL: One of the ways that the Southern Ocean influences climate is because it's home to the worlds largest ocean current, called the Antarctic circumpolar current. And it carries more water round the Antarctica than the flow of all the world's rivers combined.
So if that current warms or cools, it can have an impact on regional patterns of rainfall and temperature.
FELICITY OGILVIE: The Astrolab leaves Hobart tonight, bound for Antarctica yet again with the purpose of not only re-supplying the base but finding out more about how climate change's affecting the Southern Ocean.
MARK COLVIN: Felicity Ogilvie.