South Atlantic Dump Circulation (AMOC) ocean currents are vital for transporting heat from the tropics to the northern hemisphere, but new research suggests climate change could bring the AMOC out of action much earlier than expected.
This could have profound large-scale impacts on the planet in terms of weather patterns, agricultural practices, biodiversity, and rising economic stability in the large areas of the world that AMOC influences.
The problem is the speed at which the Earth heats up and melts ice in the Arctic: according to new models from researchers, this rate of temperature rise means that the risk of reaching the tipping point because l ‘AMOC staying dormant is now an urgent concern.
(University of Copenhagen)
“It’s worrying news,” says physicist Johannes Lohmann of the University of Copenhagen in Denmark. “Because if that’s true, it reduces our secure operating space.”
Lohmann and his partner Peter Ditlevsen adapted an existing model of ocean climate change to study the consequences of an increase in the rate of freshwater inflows into the North Atlantic Ocean, driven by the rapid melting of ice sheets of Greenland.
The model showed that a faster rate of fresh water change could cancel the AMOC much earlier. In a rate-induced tip scenario like this, the most important thing is the rate at which a change is taking place, rather than a specific threshold, and once the turning point is reached, there is no going back. .
In other words, the speed at which we expel greenhouse gases and melt ice in Greenland leaves us with very little room for maneuver in protecting the climate systems that keep global weather patterns under control. Researchers say the same problem could also threaten other climate subsystems around the world.
“These turning points have been shown previously in climate models, where melting water is introduced very slowly into the ocean,” Lohmann told Molly Taft on Gizmodo. “Actually, Greenland’s meltwater increases are accelerating and cannot be considered slow.”
The AMOC functions as a giant, looping seawater conveyor belt, redistributing water and heat around the northern hemisphere as temperature, salt, and the relative weight of the water fluctuate. It is part of the reason why European winters are relatively mild even at higher latitudes.
Although it is not clear exactly where the turning point of the AMOC is, it has been decelerating in recent years and this new study suggests that the faster climate change takes place, the more common these risks are. . Scientists think that an influx of cold fresh water from Greenland is likely to prevent warm water from spreading north.
Climate change modeling is incredibly complicated, with so many factors to consider, and Lohmann and Ditlevsen themselves admit that more work needs to be done to find out the exact details of this rate-induced tip scenario.
However, they hope that it will serve as a reminder of the urgency of action against the climate crisis: our goals to reduce greenhouse gas emissions must be as ambitious as possible, regardless of the scenario that ends up developing. in the North Atlantic. We probably have no room for error.
“Due to the chaotic dynamics of complex systems, there is no well-defined critical rate of parameter change, which severely limits the predictability of long-term qualitative behavior,” the researchers write in their work.
“The results show that the safe operating space of the elements of the terrestrial system with respect to future emissions could be smaller than previously thought.”
The research has been published in PNAS.