Melting Antarctic could impact oceans ‘for centuries’

SYDNEY: Rapidly melting Antarctic ice threatens to dramatically slow deep-water currents in the wor­ld’s oceans, scientists say, impacting the spread of fresh water, oxygen and life-sustaining nutrients for centuries.

New modelling points to faster Antarctic ice melts driving a “substantial slowdown” of water circulation in the ocean depths if global carbon emissions remain high, researchers said in a study published in “Nature” on Wednesday.

The “overturning circulation” of waters in the de­­epest reaches of the oceans would slow by 40 per cent by 2050 in a high-emissions scenario, according to the study, which warned of impacts that would last “for centuries to come”.

If the model holds true, the deep ocean current will be “on a trajectory that looks headed towards collapse”, said University of New South Wales (UNSW) climate professor Matthew England, who coordinated the study.

Trillions of tonnes of cold, highly salty and oxygen-rich water sink around Antarctica each year, sen­ding a deep-water current northward to the Indian, Pacific and Atlantic oceans, scientists say.

The greater volumes of melting ice make the Anta­rctic waters less dense and salty, however, slowing the deep-water circulation with consequences for climate, sea level and marine ecosystems. “If the oceans had lungs, this would be one of them,” England said.

And if the oceans become stagnant below 4,000 metres, “this would trap nutrients in the deep ocean, reducing the nutrients available to support marine life near the ocean surface,” he added.