Dangerous slowing of Antarctic ocean circulation sooner than expected

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PARIS - Climate change-driven shifts in the circulation of waters to the deepest reaches of the ocean around Antarctica, which could reverberate across the planet and intensify global warming, are happening decades “ahead of schedule”, according to new research.

Scientists have said that an acceleration of melting Antarctic ice and rising temperatures, driven by the emission of planet-warming gases, is expected to have a significant effect on the global network of ocean currents that carry nutrients, oxygen and carbon.

This could not only threaten marine life, but it also risks changing the ocean’s crucial role in absorbing carbon dioxide and heat.

An earlier study using computer models suggested “overturning circulation” of waters in the deepest reaches of the oceans would slow by 40 per cent by 2050 if emissions remain high.

But new research released on Thursday – based on observational data – found that this process had already slowed 30 per cent between the 1990s and 2010s.

“Our data show the impacts of climate change are running ahead of schedule,” said lead author Kathryn Gunn, of the Australian Science agency CSIRO and Britain’s Southampton University.

The implications could be significant, with Antarctica’s deep ocean acting as a key “pump” for the global network of ocean currents.

“As the ocean circulation slows, more carbon dioxide and heat are left in the atmosphere, a feedback that accelerates global warming,” said Dr Gunn.

“In some ways, the fact that this is happening isn’t surprising. But the timing is.”

Dr Gunn said previously it had been difficult to understand the changes happening in the remote region because of a lack of data and a host of challenges for scientific research, from getting funding to facing extreme conditions at sea.

The authors used observational data gathered by hundreds of scientists over decades and then “fil...

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