Melting Antarctic ice will slow down a major global deep ocean current by 40% by 2050

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Melting Antarctic ice will slow a major global deep-sea current by 40% by 2050 – and could change global climate for CENTURIES, study warns

  • Study points to possible collapse of water circulation system around Antarctica
  • It could have centuries of implications for the health of the oceans and the marine food web

Melting ice around Antarctica will cause a slowdown in a major global deep-sea current by 2050 that could have devastating consequences for the health of the oceans and the marine food web.

It could also alter the world’s climate for centuries and accelerate sea level rise, a new study suggests.

The scientists warn that if greenhouse gas emissions remain at current levels, currents in the deepest parts of the ocean could decrease by 40 percent in just 30 years.

The domino effect would deprive marine life of vital nutrients, alter weather patterns and further raise sea levels.

Emissions will need to fall rapidly this decade to avoid these potentially dire consequences, the team of Australian researchers said.

If they don’t, more marine life could go extinct, the ocean will struggle to absorb and retain heat, and ice loss will accelerate even further.

“That’s where the urgency comes from,” says CSIRO oceanographer Dr. Steve Rintoul, who helped produce the projections and has spent his entire career studying the influence of the Southern Ocean around Antarctica on Earth’s systems.

“Once we slow down the circulation, it’s hard to get it going again. Once we get this going, we can’t really change our mind. These changes are irreversible on timescales of many, many centuries.’

The world has very few places that produce water cold enough and dense enough to sink to the deepest parts of the ocean, but Antarctica has four such locations.

About 250 trillion tons of water sinks to depths less than 4,000 meters near the continent each year, and is in turn very cold, very salty and oxygenated water.

However, the increase in melting Antarctic sea ice is rlower the salinity, making the water less dense and less able to sink.

This is important because it means that the nutrient-rich water far below is not being moved in the normal way and is spreading to other locations in the deep Indian, Pacific and Atlantic Oceans.

Such is the dramatic consequences, that surface ecosystems around the world are then deprived of the nutrients of that water.

“If we limit those surging fluxes of nutrients, and we don’t provide enough nutrients to the base of the food chain … that clearly has implications for feeding the population in the coming decades, into the 21st century,” said professor at the University of NSW Matthew England, who coordinated the new study.

Dr. Rintoul says the new modeling is much more advanced than any previous work focused on Antarctica, and that means scientists can have much greater confidence in the projections.

Simulations show a slowing of the overturning circulation, which then leads to rapid warming of the deep ocean.

“Direct measurements confirm that deep ocean warming is indeed already underway,” he added.

The same is happening with the Northern Hemisphere equivalent, with the melting of the Greenland ice sheet suppressing the North Atlantic overturning, Professor England says.

“These two bodies of water (in Antarctica and the North Atlantic) absolutely dominate, in a sense, the ventilation of all ocean water below about 5,000 feet,” he said.

He added that the North Atlantic system has been shut down in the past and scientists believe it is also headed for a slowdown and possible collapse in the future.

A collapse of either system would have profound consequences for marine ecosystems worldwide, Professor England said.

The projections have been published in the journal Nature.

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