To the south of Greenland, for years, there have been an area that suffers, against all odds, a persistent cooling. In the middle of a world that is increasingly warming, that blue spot (that ‘cold bubble’) has posed a challenge for models, experts and administrations: after all, it is the only region of the global ocean that is cooling. What the hell is going on there?
Now Stefan Rahmstorfthe world’s leading expert on the collapse of the Gulf Stream, has had an idea.
A mystery in the heart of the North Atlantic? Yes and no. Indeed, to the extent that we do not know why it is there, or what mechanisms govern it, the ‘cold bubble’ is one of the great mysteries of current climate science. However, that does not mean that we have not studied it. On the contrary, we have done it to the point of satiety.
This oceanic anomaly is, almost certainly, one of the most studied in the last decade. The novelty is not in the phenomenon itself: we have known about it since the mid-90s. The novelty is in the explanation.
Do we already know why it happens? We now have a new explanation that makes sense and is plausible; but it is still controversial. Rahmstorf’s team has carried out an analysis of the heat balance in that region of the Atlantic.
And their conclusions are that the decrease in heat of the entire water column is not explained by surface flows. In fact, the area that loses the most heat does not coincide with the area that loses the most surface heat. With this in mind, they begin to raise hypotheses and discard them.
This is how they arrive at the idea that the cooling comes from a reduction in oceanic heat transport to the region. That is, of a weakening of the AMOC.
We have been talking about the death of the AMOC for years, has no one thought of this? Yes, indeed, this was one of the main working hypotheses. But until now everything was worked with indirect models. It is now that Rahmstorf’s team has been able to draw the complete scheme and detect a link that, it seems, is due to the multidecadal evolution of the Current with the Ocean.
Why do I say it is controversial? To begin with, because like any scientific study it is subject to reanalysis, discussions and counterarguments. But, above all, because Rahmstorf and his team are specialists in exactly what they have found.
For many climatologists there is a certain risk that this work falls short of the popular saying that “for those who have hammers, everything is nails.” Rahmstorf has linked his intellectual figure to the collapse of the AMOC and that, inevitably, raises suspicions.
However, today (and with the data we have) it may be one of the best explanations we have. not the only onebut in these topics we almost never have a single (almost) satisfactory explanation.
So, is the AMOC going to collapse? Let us remember that the Atlantic Meridional Overturning Circulation (AMOC) is the North Atlantic branch of the thermohaline circulation. Since the sun does not heat the sea equally everywhere and freshwater flows reach the ocean at very specific points, this is the basic mechanism by which the oceans balance differences in temperature and salinity.
The AMOC is a fundamental mechanism for Europe’s climate and economy. “Without it, Western Europe and eastern North America would cool significantly, with a host of potential adverse effects,” said Sánchez Laulhé.
However, scientists cannot agree on what will happen. In 2021, the IPCC said the AMOC was “unlikely” to collapse. In 2023, the Ditlevsens not only said that it was a probable scenario, but that they set the first date for the collapse. In 2024, 44 signatories They asked to take the problem seriously. But in January 2025 Terhaar, Vogt and Foukal said which, in short, had not weakened since 1063.
The reasonable thing to say is that yes, climate drift seems to suggest that at some point the AMOC will collapse. It has already happened other times. The impossible is to say when, how and why.
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