Scientists warn that deep-ocean water flows from Antarctica could drop by 40 percent by 2050, threatening to collapse the circulation crucial to planetary systems.
New research says the rapid melting of Antarctic ice is dramatically slowing the flow of water through the world’s oceans and could have a catastrophic effect on the global climate, the marine food chain, and even the stability of ice shelves.
The ocean’s “overturning circulation” – driven by the movement of denser water toward the sea floor – helps provide heat, carbon, oxygen and vital nutrients around the world.
However, deep ocean water flows from the Antarctic could decrease by 40 percent by 2050, according to a study published Wednesday in the journal Nature magazineThat warned the effects could last “for centuries to come”.
“It’s amazing to see this happening so quickly,” said Alan Meeks, an Oregon State University paleoclimatologist and co-author of the latest IPCC assessments, who was not involved in the study.
“Looks like he’s starting to move now. That’s the headline news.”
University of New South Wales (UNSW) climate professor Matthew England, who coordinated the study, said that if the model was correct, the deep ocean current would be “on a crash course”.
As temperatures rise, fresh water from melted Antarctic ice enters the ocean, reducing the salinity and density of surface waters and reducing downward flow to the sea floor.
While previous research has looked at what might happen to a similar upturn in the North Atlantic — the mechanism behind a doomsday scenario that would see Europe experience an Arctic blowout as heat transport falters — not much has been done on the Antarctic floor’s water circulation. .
Scientists relied on about 35 million computing hours over two years to spin a variety of models and simulations through the middle of this century, and found that circulation of deep waters in the Antarctic could spur twice the rate of decline in the North Atlantic.
John Church, professor emeritus at the University of New South Wales, who was not involved in the study, said there is a lot of uncertainty about the impact of the decline in circulation in the deep ocean.
“But it seems almost certain that continuing on a path of elevated greenhouse gas emissions will lead to more profound effects on the ocean and the climate system,” Church said.
“The world urgently needs to significantly reduce our emissions to get off the high emissions path we are currently on.”
The study team included lead author Qian Li from MIT and co-authors from the Australian National University and the Australian Commonwealth Scientific and Industrial Research Organization (CSIRO).
England said the impact of meltwater on global ocean circulation is not yet included in the complex models used by the Intergovernmental Panel on Climate Change to describe future climate change scenarios, but it will be significant.
The ocean upturn allows nutrients to rise from the bottom with the Southern Ocean supporting about three-quarters of global phytoplankton production, the base of the food chain, said another co-author of the study, Steve Rintoul.
“If we slow down the sinking near Antarctica, we slow down the whole circulation, and so we also reduce the amount of nutrients coming back from the ocean depths to the surface,” said Rintoul, the CSIRO fellow.
The study results also indicate that the ocean will not be able to absorb as much carbon dioxide as its upper layers become more layered, leaving more carbon dioxide in the atmosphere.
The study showed that warmer water intrusion into the West Antarctic Ice Shelf would increase, but did not look at how this might create a backflow effect and generate more melt.
“It does not include disaster scenarios,” Meeks said. “In that sense, it’s actually kind of conservative.”
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