New research shows the Southern Ocean is storing more heat than any other ocean in the world.
The study, carried out by Tasmania’s Antarctic Climate and Ecosystem centre, has found that carbon dioxide levels in the Southern Ocean will be corrosive to some shellfish by 2030 if current trends continue.
Scientists say deep moving currents around Antarctica are the reason why the Southern Ocean is warming faster than other oceans.
“The Southern Ocean occupies about 22 per cent of the area of the total ocean, and yet it absorbs about 40 per cent of the carbon dioxide that’s stored by the ocean and about half the heat that’s stored by the ocean,” climate scientist Steve Rintoul says.
Dr Rintoul says the warming extends for four kilometres, from the ocean surface to the sea floor.
He says satellite measurements show the Southern Ocean has been warming by about 0.2 degrees Celsius per decade.
“One of the impacts of a warming ocean may be that the ice that flows off Antarctica into the ocean may melt more rapidly,” he said.
“Once that ice reaches the ocean and is floating, if we melt it, it doesn’t change the sea level because that ice is already floating, just like an ice cube in your drink, when it melts it doesn’t cause the cup to overflow.
“But what does happen is that as the ice floating around the edge of Antarctica thins and breaks up and disappears, the ice that’s on the continent slides off the continent into the sea more rapidly, and that does increase sea level rise.
“In the last few years we found that some parts of Antarctica are thinning rapidly, indicating that ice is flowing off the continent into the ocean and causing an increase in sea level.”
The Southern Ocean has helped absorb the Earth’s excess heat and carbon dioxide.
But Dr Rintoul says as carbon dioxide dissolves, it changes the chemistry of sea water.
“As we dissolve carbon dioxide in the ocean we change the chemistry and eventually we’ll cross the threshold between waters [where] the shells are stable, and waters where the sea water’s actually corrosive to the shell material and starts to dissolve the shells that the animals are making,” he warned.
“We used to think that threshold would be crossed in about 2050 in the Southern Ocean. We now understand that that’s likely to happen a few decades earlier, perhaps as soon as 2030.
“This is important in part because animals that make these shells are important prey for bigger animals like whales.”
The research is a collation of more than 40 peer-reviewed publications.