Fears that Antarctic Ocean is headed for ‘Day After Tomorrow’ disaster moment

Antarctica’s deep ocean current, which has been relatively stable for thousands of years, is at risk of slowing down in the next three decades – with serious implications for the entire planet, scientists have warned.

Deep water currents in the Antarctic, known as “overturning circulation”, travel around the world carrying heat, carbon, oxygen and nutrients, playing an essential role in stability of climate, sea levels and marine ecosystems.

But the rising global temperature, caused by carbon emissions, is melting ice caps around the South Pole and dumping vast quantities of freshwater into the ocean, making it less salty and dense.

The new scientific modelling reveals that this could slow down deep water circulation more than 40 per cent by 2050 – putting it on a path towards collapse, said Professor Matthew England, deputy director of the ARC Centre for Excellence in Antarctic Science (ACEAS), at the University of New South Wales (UNSW).

The team from UNSW, the Massachusetts Institute of Technology, Australian National University and CSIRO, Australia’s governmental scientific research agency, published the landmark study in the journal Nature on Wednesday.

“Our study shows that the melting of the ice sheets has a dramatic impact on the overturning circulation that regulates Earth’s climate,” says Dr Adele Morrison, also from ACEAS and the ANU Research School of Earth Sciences.

With collapse of the deep current, oceans below 13,000 feet (4,000 metres) would stagnate and cause impacts for centuries.

“This would trap nutrients in the deep ocean, reducing the nutrients available to support marine life near the ocean surface,” Prof England said, in a statement.

The Australian Science Media Centre evoked the sci-fi disaster movie, The Day After Tomorrow, which tells the fictional story of global catastrophe caused by collapse of the North Atlantic Ocean circulation.

The new study’s scientific modeling is based on a “high emissions scenario” – a global trajectory if countries fail to cut (still-rising) emissions in the coming decades. Melting of the polar ice sheets is expected to accelerate as the planet heats up.

“Any significant change to the overturning circulation would have profound effects,” said Emeritus Professor John Church, from UNSW’s Climate Change Research Centre, who was not part of the study.

He noted that previous studies have mostly focused on the north Atlantic Meridional Overturning Circulation, leaving the Antarctic Ocean relatively under researched.

“Many uncertainties remain about the impact beyond 2050, including the potentially larger loss of mass from Antarctica postulated in some studies,” Professor Church added.

“But it seems almost certain that continuing on a high greenhouse gas emission pathway will lead to even more profound effects on the ocean and the climate system. The world urgently needs to drastically reduce our emissions to get off the high emission pathway we are currently following.”