Imagine looking out from the Dutch coast and finding the North Sea completely frozen. A truly chilling scenario more suited to science fiction films than a real possibility. Or at least we believed so until a few years ago. Today, however, there is more and more confirmation that the collapse of the Gulf Stream is probable between 2025 and 2095. An estimate which, according to a new study, has a confidence index of 95%. So not only is it certain that we are about to tell you it will happen, but it is likely that it will happen within this century and as early as next year. The consequences: a complete revolution of the world as we know it, with the collapse of entire climate systems in the space of a few decades (in the image below the extension of the polar ice pack in the next century). But let’s try to go step by step using the words of science and not catastrophism.
The “southern overturning of the Atlantic circulation” (Atlantic meridional overturning circulation, acronym Amoc) is the name with which scientists indicate the oceanic circulation that transports water and heat from the tropics towards the more northern latitudes, and from which the famous current originates of the gulf which guarantees a temperate climate to our continent. As we told you last year, climate scientists fear that these ocean currents are at risk due to the melting of Greenland’s ice. The effects on the European climate would be important, and sudden as confirmed by a new study published in Science Advances by researchers at Utrecht University. For the first time it was possible to replicate the collapse of the southern overturning of the Atlantic circulation even with a cutting-edge global climate model, confirming that the point of no return could be ever closer.
The collapse of Amoc, what are we talking about
The meridional reversal of the Atlantic circulation is part of a larger phenomenon known as the global thermohaline circulation, a sort of enormous highway that winds throughout the oceans redistributing heat between the poles and the equator. Lately we have been hearing about it often, because it is feared that the AMOC is in a slowing down phase: the melting of the Greenland ice, in fact, reduces the salinity of the ocean precisely at the point where the warm and saline water coming from the gulf of Mexico, as it cools, it becomes denser and sinks deeper, fueling the southern reversal of the Atlantic circulation.
The more fresh water trapped in the ice is released into the ocean, the greater the risk that the global circulation mechanism will fail, leading to the collapse of the AMOC and the Gulf Stream.
It is believed that in the distant past it happened several times, causing the cooling of Europe and North America, and the warming of the Southern Hemisphere. And for this reason, there is a fear that the slowdown observed in recent decades could actually represent an alarm signal, which heralds the approach of a point of no return. Something like this has been observed since the 1990s with relatively rudimentary climate models, and until today it had not yet appeared in the more refined modeling, which takes into account the processes underway in both the oceans and the atmosphere to predict the evolution of our planet’s climate system. This is evidently where the new research comes into play.
Model
Dutch researchers used the supercomputer of the Dutch National Supercomputing Facility for six months to run a cutting-edge climate model that simulated 4,400 years of evolution of the Earth’s climate, slowly and gradually increasing the influx of fresh water from from the melting of the ice in Greenland. In this way, for the first time, they managed to model a scenario in which the collapse of the meridional overturning of the Atlantic circulation actually appeared, and were therefore able to study which alarm bells precede the reaching of the point of no return, beyond which is AMOC destined to stop, and what consequences would there be on the planet’s climate?
According to the Dutch researchers, it is currently impossible to predict when we might reach it, but their simulations are compatible with a collapse of Amoc by the end of the century, starting from 2025. If that happened, what would be the consequences?
In Europe, temperatures would drop rapidly, even by 3 degrees per decade (currently global warming is increasing them by around 0.2 per decade) over the space of about a century. Extremely harsh winters would therefore arrive in the northernmost regions, with temperatures that in a country like Norway could drop by as much as 20 degrees compared to the current ones, while in countries like Italy we are talking about a few degrees less than those we see today . The effects would therefore not be catastrophic hypothesized in a film like Day After Tomorrow, in which following the collapse of Amoc, North America became completely uninhabitable. But these would still be important climate changes, and as the authors of the study warn, they would also have consequences on other phenomena, such as the rise of the oceans and precipitation, with the risk of further accelerating the ongoing climate changes.
According to the maps published in the study, in addition to the extension of the Arctic ice pack up to part of the North Sea, there would also be a collapse in rainfall in Southern Europe, deprived of the supply of humid air that arrives thanks to the “conveyor belt” of the Arctic current. Gulf.
