Scientists believe that the deep ocean currents that are emerging around Antarctica and that have an impact on global temperature, sea level, and marine ecosystems are on the verge of extinction
Deep ocean currents forming around Antarctica, that impact climate, sea level and marine ecosystems around the world, are headed for a collapse, according to scientists.
Such a decline would stagnate the bottom of the oceans and affect climate and marine ecosystems for centuries to come, they said.
"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," said Matthew England, University of New South Wales (UNSW), Sydney, Australia, who coordinated the international study.
The work is published in the journal Nature.
About 250 trillion tonnes of cold, salty, oxygen-rich water sinks near Antarctica each year and drives the deepest flow of the overturning circulation - a network of currents spanning the world's oceans.
The Antarctic overturning carrying heat, carbon, oxygen and nutrients, spread northwards into the deep Indian, Pacific and Atlantic Oceans, influencing global climate, sea level and the productivity of marine ecosystems.
"If the oceans had lungs, this would be one of them," said England.
The modelling of Antarctic deep water until 2050, produced under the Intergovernmental Panel on Climate Change (IPCC) 'high emissions scenario', captured unprecedented detail of ocean processes, including the impact of predictions for meltwater from ice on circulations.
The study found that melting ice around Antarctica, which is expected to continue accelerating as the planet warms, makes the nearby ocean waters less dense, slowing the Antarctic overturning circulation.
"We are talking about the possible long-term extinction of an iconic water mass," said England.
Significant slowdown of the Antarctic overturning is expected over the next few decades, owing to increasing greenhouse gas emissions, even as the overturning has remained largely stable for thousands of years.
"Such profound changes to the ocean's overturning of heat, freshwater, oxygen, carbon and nutrients will have a significant adverse impact on the oceans for centuries to come," said England.
With a collapse of this deep ocean current, the oceans below 4000 metres would stagnate, the scientists said.
"This would trap nutrients in the deep ocean, reducing the nutrients available to support marine life near the ocean surface," said England.