Atlantic Ocean circulation: Europe will become 15°C colder in a few decades

Atlantic Ocean circulation distributes heat, nutrients and oxygen between Europe, Africa and the Americas

(sustainabilityenvironment.com) – Imagine a giant conveyor belt running through the entire Atlantic Ocean from South Africa to Greenland and Europe and vice versa. A global system that distributes heat, oxygen and nutrients between three continents and the sea that separates them. It is to its existence that this part of the Planet owes its climate. Including the mild temperatures, given the latitude, that we have in Europe. Many studies in recent years have clarified that this mechanism – the Atlantic Ocean circulation or Atlantic meridional overturning circulation (AMOC) – is slowing down. But it was, according to the authors, a slow process. A new work published in Science Advances corrects them: the collapse of AMOC will be very rapid, less than a century. And it won’t leave us much chance to adapt to the new climate that comes.

Warning signs

To determine this, researchers at the University of Utrecht in the Netherlands have identified a new warning sign that will help us understand how the collapse of AMOC is happening. It is based on the analysis of the salinity of the waters in the extreme south of the Atlantic Ocean. The difference in salinity (and temperature) is precisely the “motor” of the Atlantic meridian circulation, which allows the currents to overturn and travel thousands of kilometers from North to South (thermohaline circulation).

The indicator confirms the results of previous studies: AMOC is slowing down. This is already consolidated data, so much so that the latest report of the IPCC released in 2021 claims that it is “very likely” that the Atlantic meridian circulation will continue to lose speed until 2100. But he believes that there is only an “average probability” that its collapse will occur already during this century, even if from the 50s to today it has lost 15% of its strength.

Some recent works, including a study published last July, claim instead that the stop is around the corner and could begin to occur as early as 2025, or more likely during the 50s of this century.

What happens if the Atlantic Ocean circulation stops?

The study published in Science Advances does not speculate on when the collapse might occur but brings solid elements about how the collapse will occur. It is just as important, if not more important. Because the predictive model used by Utrecht researchers shows that it will be exceptionally quick. The bulk of the stop will last about 100 years, but the greatest effects on the planet’s climate will be felt throughout a couple of decades. It is such a high speed that it becomes practically impossible for humanity to adapt to change without profound social, economic and possibly even political consequences. Because the scope of change would be very broad and would touch the very foundations of our societies. Starting from the production of food, which would be upset by a climate so different from that of 20 years before.

What are the concrete changes that should occur with a sudden collapse of the Atlantic meridional overturning circulation ?
Europe would be among the most affected regions, with a collapse in average temperatures of up to 10ºC in the western part and much less rainfall. The change would affect all seasons. Putting European agriculture at great risk. Many European cities will have temperatures 5-15 °C levels, and they will get there by losing an average of 3 ºC per decade. It’s a truly apocalyptic scenario. Just compare it to the pace of global warming today: it advances by about 0.2 ºC every 10 years. The AMOC stop would trigger changes 15 times faster.

In the Amazon, the result of the collapse of AMOC would be the reversal of dry and wet seasons. An event that could accelerate the trigger of the point of no return of the tropical forest, thus decreeing a long agony of an ecosystem crucial for carbon storage. In general, annual temperatures around the globe would be much more fluctuating: that is, extremes of heat and cold would be more intense and frequent. The southern hemisphere, unlike Europe, would become warmer on average.

“We’re on the verge of collapse, but we’re not sure how close,” explains study principal Rene van Westen. “We are heading for a point of no return“.