SYDNEY: The latest report has warned that rapidly melting Antarctic ice is causing a substantial slowdown in deep ocean currents and could have disastrous consequences on the climate.
A team of Australian scientists said that the deep-water flows that drive ocean currents could decline by 40 percent by 2050.
The currents carry vital heat, carbon, oxygen and nutrients worldwide.
The previous research proposes that a slowdown in the North Atlantic current could cause Europe to become colder.
The study, published in the journal Nature, warns that the slowdown could decrease the ocean’s ability to absorb carbon dioxide from the atmosphere.
The report headlines how the descending movement of cold, dense saltwater towards the sea bed near Antarctica partly drives the Earth’s network of ocean currents.
But as the fresh water from the ice cap melts, seawater becomes low salty and dense, and the downward movement slows.
Scientists say these deep ocean currents and “overturnings” in the northern and southern hemispheres have been relatively stable for thousands of years, but the warming climate is now disrupting them.
Study lead Professor Matthew England said that “Our modelling shows that if world carbon emissions continue at the current rate, then the Antarctic overturning will slow by more than 40% in the next 30 years and on a trajectory that looks headed towards collapse,”
“If the oceans had lungs, this would be one of them,” Professor England, the oceanographer at Sydney’s University of New South Wales, told a news briefing.
Dr Adele Morrison explained that as ocean circulation slowed, water on the surface quickly reached its carbon-absorbing capacity and was then not replaced by non-carbon-saturated water from greater depths.
The Atlantic Ocean circulation system
The 2018 Atlas Study found that the Atlantic Ocean circulation system was weaker than it had been for thousands of years and had changed significantly in the past 150.
It recommends changes to the conveyor-belt-like Atlantic Meridional Overturning Circulation that could cool the ocean and northwest Europe and affect deep-sea ecosystems.
The sensationalised depiction of the Amoc shutting down was shown in the year 2004 climate disaster film The Day After Tomorrow.
But Morrison said a slowdown in the southern overturning would’ve more of the collision on marine ecosystems and Antarctica itself.
“Overturning brings up nutrients that have to go down to the bottom when organisms die… to resupply nutrients for the world ecosystem and fisheries,” she told the BBC.
“Another larger implication that it could have is feedback on how much of Antarctica melts in the future. When this overturning slows, it opens a pathway for warmer waters which could cause increased melt, which would be further feedback, putting more meltwater into the ocean and slowing down this circulation even more,” she added.
The Scientists spent 35 million computing hours over two years to produce their models, which recommend deep water circulation in the Antarctic could slow at twice the rate of reduction in the North Atlantic.
“[It’s] stunning to see that happen so quickly,” said climatologist Alan Mix from Oregon State University, a co-author of the latest Intergovernmental Panel on Climate Change (IPCC) assessment.
“It appears to be kicking into gear right now. That’s outline news,” he told Reuters.
The effect of Antarctic meltwater on ocean currents has not yet been factored into IPCC models on climate change, but it will be “considerable”, Prof England said.
