Antarctic ocean currents heading for collapse- report

Rapidly melting Antarctic ice is causing a dramatic slowdown in deep ocean currents and could have a disastrous effect on the climate, a new report warns.

The deep-water flows which drive ocean currents could decline by 40% by 2050, a team of Australian scientists says.

The currents carry vital heat, oxygen, carbon and nutrients around the globe.

Previous research suggests a slowdown in the North Atlantic current could cause Europe to become colder.

The study, published in the journal Nature, also warns the slowdown could reduce ocean's ability to absorb carbon dioxide from the atmosphere.

The report outlines how the Earth's network of ocean currents are part driven by the downwards movement of cold, dense saltwater towards the sea bed near Antarctica.

But as fresh water from the ice cap melts, sea water becomes less salty and dense, and the downwards movement slows.

These deep ocean currents, or "overturnings", in the northern and southern hemispheres have been relatively stable for thousands of years, scientists say, but they are now being disrupted by the warming climate.

"Our modelling shows that if global carbon emissions continue at the current rate, then the Antarctic overturning will slow by more than 40 per cent in the next 30 years - and on a trajectory that looks headed towards collapse," study lead Professor Matthew England said.

"If the oceans had lungs, this would be one of them," Prof England, an oceanographer at Sydney's University of New South Wales, told a news briefing.

Dr Adele Morrison, who contributed to the report, explained that as ocean circulation slowed down, water on the surface quickly reached its carbon-absorbing capacity and was then not replaced by non carbon-saturated water from greater depths.