- by Tom Housden
- BBC News, Sydney
A new report warns that the rapid melting of Antarctic ice is causing a significant slowdown in deep ocean currents and could have a catastrophic impact on climate.
A team of Australian scientists says the deep water flows that drive ocean currents could drop by 40% by 2050.
Currents carry vital heat, oxygen, carbon and nutrients around the world.
Previous research suggests that a slowdown in the North Atlantic Current may be causing Europe to cool.
The study, published in the journal Nature, also warns that the slowdown may reduce the ability of the oceans to absorb carbon dioxide from the atmosphere.
The report shows how Earth’s network of deep ocean currents is driven by the movement of cold, dense, salty water toward the seafloor near Antarctica.
But as fresh water from the ice sheet melts, sea water becomes less salty and dense, and downward movement slows.
Scientists say this deep ocean current, or “inversion,” has been relatively stable for thousands of years, but is now being disrupted by a warming climate.
“Our models show that if global carbon emissions continue at the current rate, the Antarctic reversal will slow by more than 40 per cent in the next 30 years – and on a trajectory that appears to be heading for collapse,” said Professor Matthew England, lead study author of the study. .
“If the oceans had lungs, it would have had one,” Professor England, an oceanographer at the University of New South Wales, Sydney, told a news briefing.
The scientists spent 35 million computing hours over two years producing their models, which suggests that circulation of deep waters in the Antarctic could slow twice the rate of decline in the North Atlantic.
It suggested that changes in the conveyor-belt-like Atlantic overturning circulation (Amoc) could cool the ocean and northwestern Europe, and affect deep-sea ecosystems.
The results of the latest study also indicate that a slowdown in circulation will also mean that the ocean cannot absorb as much carbon dioxide from the atmosphere because its upper layers have become “stratified”.
Professor England warned that water below 4,000 meters (13,123 ft) would stagnate and prevent vital ocean nutrients from reaching marine life.
“[It’s] It’s amazing to see this happen so quickly, said climate scientist Alan Meeks of Oregon State University, a co-author of the latest IPCC assessment.
“It looks like he’s on the move now. This is major news,” he told Reuters.
England said the impact of Antarctic meltwater on ocean currents had not been factored into the IPCC’s models of climate change, but would be “significant”.
The study also highlighted how warming oceans could lead to greater melting of the West Antarctic Ice Shelf, but did not examine how this might lead to a feedback effect, and even more melting.
“Web maven. Infuriatingly humble beer geek. Bacon fanatic. Typical creator. Music expert.”
Astronauts’ brains are affected during long spaceflights
Scientists discover the “lost world” in a billion-year-old Australian rock | Science and technology news
Time-Lapse shows the first live broadcast from Mars