Simone Valesini February 16, 2024
Imagine looking out from the Dutch coast and finding the North Sea completely frozen over. A truly scary scenario, more suitable for science fiction films than a real possibility. At least that's what we believed until a few years ago. However, today there is increasing confirmation that the Gulf Stream collapse is likely between 2025 and 2095. An estimate that, according to a new study, has a 95% confidence index. So not only is it certain that we will tell you it will happen, but it is also likely that it will happen later 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 within a few decades (in the picture below, the expansion of polar ice in the next century). But let's try to go step by step, using the words of science and not catastrophism.
Scientists call the “southern overturning of the Atlantic circulation” (Atlantic meridional overturning circulation, acronym Amoc) the oceanic circulation that transports water and heat from the tropics to the more northern latitudes and from which the famous current comes from the Gulf, which gives our continent a temperate Climate guaranteed. As we told you last year, climate scientists fear that these ocean currents are threatened by melting Greenland ice. The impact on Europe's climate would be significant and sudden, a new study published in Science Advances by researchers at Utrecht University confirms. For the first time, it was possible to reproduce the collapse of the southern overturn of the Atlantic circulation even with a state-of-the-art global climate model, confirming that the point of no return may be getting closer and 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 kind of giant highway that winds through the oceans and redistributes heat between the poles and the equator. We're hearing about this a lot lately because of fears that the AMOC is in a slowing phase: the melting of the Greenland ice cream is actually reducing the salinity of the ocean right where the warm and saline water from the Gulf of Mexico is increasing Cooling becomes denser and sinks deeper, driving the southward reversal of the Atlantic circulation.
The more fresh water trapped in ice enters the ocean, the greater the risk that the global circulation mechanism will fail and the AMOC and Gulf Stream will collapse.
This is believed to have occurred several times in the distant past, causing the cooling of Europe and North America and the warming of the Southern Hemisphere. And for this reason, there are fears that the slowdown observed over the last few decades could actually represent an alarm signal that heralds the approaching point of no return. Something like this has been observed since the 1990s using relatively rudimentary climate models, and until today it had not yet appeared in the more refined modeling that takes into account the processes occurring in the oceans and atmosphere to predict the evolution of our planet's climate system. This is apparently where the new research comes into play.
Model
Dutch researchers used the Dutch National Supercomputing Facility's supercomputer for six months to run a state-of-the-art climate model that simulated the evolution of Earth's climate over 4,400 years, slowly and gradually increasing the inflow of fresh water from melting ice in Greenland. In this way, they managed for the first time to model a scenario in which the collapse of the meridional overturning of the Atlantic circulation actually occurred, and were thus able to study which alarm bells precede the reaching of the point of no return, with which AMOC should be stopped and which ones Would that have consequences for the planet's climate?
According to the Dutch researchers, it is currently impossible to predict when we might reach this goal, but their simulations are consistent with a collapse of Amoc by the end of the century, starting in 2025. If that were to happen, what would be the consequences?
In Europe, temperatures would fall rapidly within about a century, even by 3 degrees per decade (currently global warming is increasing at about 0.2 degrees per decade). Therefore, extremely harsh winters would occur in the northernmost regions, with temperatures that could drop by up to 20 degrees compared to the current ones in a country like Norway, while in countries like Italy we are talking about a few degrees less than what we see today. The effects would therefore not be catastrophic, assuming a film like Day After Tomorrow, where North America became completely uninhabitable after the collapse of Amoc. But these are still significant climate changes and, as the study authors warn, they also have an impact on other phenomena such as rising oceans and precipitation, with the risk of further accelerating ongoing climate changes.
According to the maps published in the study, in addition to the expansion of the Arctic ice pack to part of the North Sea, there would also be a decrease in precipitation in southern Europe, as this would deprive the supply of moist air from the “conveyor belt” of the Arctic current. Golf.