Circulation of the Atlantic Ocean is heading for a tipping point that is “bad news for the climate system and humanity”, a study has found.
The scientists behind the research said they were shocked by the predicted speed of the decline once the tipping point was reached, although they said they could not yet predict how soon it would happen.
Using computer models and past data, the researchers developed an early warning indicator for the breakdown of the Atlantic Meridional Overturning Circulation (AMOC), a vast system of ocean currents that is a key component of global climate regulation.
They found that Amok was already on track toward a sudden change that hadn't happened in more than 10,000 years, and that would have dire implications for large parts of the world.
The Amok, which includes part of the Gulf Stream and other powerful currents, is an ocean conveyor belt that transports heat, carbon and nutrients from the tropics to the Arctic Circle. It cools down and sinks into the deep ocean. This temptation helps distribute energy around the Earth and moderates the impact of human-caused global warming.
But the system is eroding as Greenland's glaciers and Arctic ice melt faster than expected, pouring fresh water into the ocean and preventing saltier, warmer water from sinking in from the south.
Amok has declined 15% since 1950 and is at its weakest in more than a millennium, according to previous research, prompting speculation of an impending collapse.
There is still no consensus on how severe this should be. A study last year, based on sea surface temperature changes, It suggested that the tipping point could occur between 2025 and 2095. however, The UK Met Office said large, rapid changes in Amok were “highly unlikely”. In the 21st century.
new paper, Published in Science Advances, has broken new ground by searching for warning signs in salinity levels in the southern part of the Atlantic Ocean between Cape Town and Buenos Aires. Computer models of global climate simulating changes over 2,000 years show that a slow decline could lead to a sudden decline within 100 years, with catastrophic consequences.
The paper said the results provided a “clear answer” to whether such a sudden change was possible: “This is bad news for the climate system and for humanity. One might think that the amok tipping is only a theoretical concept and that the tipping will disappear. The entire climate system, with all its additional feedbacks, has been considered.
It also mapped some of the effects of the run amok collapse. Sea levels in the Atlantic could rise by a meter in some areas, submerging many coastal cities. Wet and dry seasons will flip in the Amazon, pushing the already fragile rainforest past its own tip. Temperatures around the world can fluctuate very erratically. The Southern Hemisphere will become warmer. Europe will cool dramatically and have less precipitation. While this may seem attractive compared to the current warming trend, the changes will hit 10 times faster than they are now, making adaptation nearly impossible.
“What surprised us was the rate at which tipping occurred,” said the paper's lead author, René van Westen of Utrecht University. “It would be catastrophic.”
There isn't enough data yet to say whether this will happen in the next year or the next century, but when it does, Changes are irreversible on human timescales.
Meanwhile, the direction of travel is undoubtedly in a dangerous direction.
“We're moving towards it. It's scary,” Van Westen said. “We need to take climate change very seriously.”