A key Atlantic current system that affects weather around the world could collapse as early as the late 2030s, scientists argue in a new study — a planetary-scale catastrophe that would transform weather and climate. Probably also in the whole world weather phenomena are often interrelated.
Several studies in recent years have indicated that the critical system – the Atlantic Meridional Turning Circulation, or AMOC – could be on the verge of collapse, weakened by warmer ocean temperatures and disturbed salinity caused by anthropogenic climate change.
But the new research, which is peer-reviewed and has not yet been published in a journal, uses a state-of-the-art model to estimate when it might break, suggesting a disruption could occur between 2037 and 2064. This research shows it is very likely to collapse before 2050.
“This is really worrying,” said Rene van Westen, a marine and atmospheric researcher at the University of Utrecht in the Netherlands and co-author of the study.
“All the negative side effects of human-caused climate change will continue to exist, like more heat waves, more droughts, more floods,” he told CNN. “So if we also have an AMOC collapse, the climate will become even more distorted.”
Water recycling cools the Southern Hemisphere and warms the North Atlantic
Like a (airport) conveyor belt, the AMOC draws warm surface water from the Southern Hemisphere and the tropics and distributes it into the cold North Atlantic. The cooler, saltier water then sinks and flows south. This mechanism prevents parts of the Southern Hemisphere from overheating and parts of the Northern Hemisphere from freezing, while distributing life-sustaining nutrients to marine ecosystems.
The effects of an AMOC collapse would be “catastrophic.” In the decades after the collapse, the Arctic ice would begin to creep south, and after 100 years it would reach the southern coast of England. The average temperature of Europe would fall, as well as North America – including parts of the United States. The Amazon rainforest would see a complete reversal of its seasons – the current dry season would become the rainy months and vice versa.
AMOC collapse “is a really big risk that we have to do everything we can to avoid,” said Stefan Ramstorf, a physical oceanographer at the University of Potsdam in Germany, who was not involved in the latest research. However, we end up experiencing unprecedented greenwashing.
To reach their conclusions, Utrecht scientists used state-of-the-art models and for the first time identified an area of the South Atlantic Ocean as the best place to monitor changes in circulation and use observational data. There they looked at ocean temperatures and salinity to confirm earlier predictions about when the AMOC might reach its tipping point.
We stare the disaster in the face and yet do nothing
Ramstorff said the emphasis on ocean exploration at the time of the collapse is a relatively new development. But it shows how far scientists’ understanding of the weakening of the AMOC has come. “Up until a few years ago, we were talking about whether it would happen at all, as kind of a low-probability, high-impact risk,” he told CNN. “And now it seems much more likely than a few years ago that this will happen. Now people are starting to get closer to when it will happen.”
Ramstorf said that about five years ago he would have agreed that an AMOC collapse this century was unlikely, although even a 10% risk was still unacceptably high “for a catastrophic effect of this magnitude”.
“There are now five papers, basically, that suggest it could very well happen in this century, or even by mid-century,” Ramstorf said. “My overall assessment now is that the risk of us passing the tipping point in this century is probably even greater than 50%.” While advances in research into the AMOC have been rapid, and models trying to predict its collapse have progressed at breakneck speed, they are still not without problems.
For example, the models do not consider a critical factor in the collapse of the AMOC – the melting of the Greenland ice sheet. Huge amounts of fresh water are breaking off from the ice sheet and flowing into the North Atlantic, disrupting one of the circulation’s driving forces: salt. “We already have a huge influx of fresh water into the North Atlantic that will completely disrupt the system,” Ramstorf said.
This research gap means that predictions could underestimate how soon or quickly a collapse will occur, Ramstorff said.