#AMOC is the reason for Europe’s temperate climate. Evidence has been accumulating over the years that it is slowing down; It is now likely to be at its weakest point in at least a millennium, and could even be approaching a tipping point. Here I will show you the latest high-resolution images and also discuss whether there is serious evidence that speaks against the current weakening of AMOC.
Our regular readers know very well the Atlantic Meridional Reversal Circulationeither AMOC in short, a large-scale overturning motion of water across the entire Atlantic carrying a quadrillion watts (i.e. 1015 W) of heat towards the North Atlantic, partly through the Gulf Stream. (If you are new to the topic, check out this article.)
AMOC instabilities have produced some of the most dramatic climate changes in recent Earth history, well known to paleoclimatologists (see, for example, my old review in Nature 2002), and concern that we are destabilizing it by causing global warming has risen sharply in expert circles in recent years (see last year’s report). open letter from 44 experts).
One reason is what we are seeing in the North Atlantic. And another reason is the latest model simulations carried out by the Dutch research group in Utrecht. A recent article by van Westen et al. (2025) has shown that the much-feared tipping point at which the AMOC breaks down (first demonstrated in a simple box model in 1961) is also found in a high-resolution (eddy-resolution) ocean model, destroying any hope that it may be an artifact of overly crude and simple models. This tipping point has been consistently demonstrated across the spectrum of models so far, and the cause is well understood (a destabilizing salt transport feedback).
Furthermore, the model and paper simulation provide us with the AMOC ‘footprint’ on sea surface temperature (SST) in unprecedented detail. So let’s take a look (Fig. 1)!
Figure 1. Pattern of sea surface temperature change caused by AMOC closure in a high-resolution ocean model. This is a pure AMOC effect without any greenhouse gas climate change. We see the famous ‘cold spot’ in blue due to less heat being carried into the North Atlantic, and also in red the shift of the Gulf Stream northward, an effect of the ocean dynamics of the weakening of AMOC (Zhang 2008). Fountain: van Westen et al. 2025., mapped by Ruijian Gou.
And now compare that fingerprint pattern to the trend in satellite measurements of sea surface temperature (Fig. 2). What do you see?
Figure 2. Normalized satellite sea surface temperature trend 1993-2021 (linear trend over that period). Normalized means divided by the global trend in mean sea surface temperature to remove the global warming signal. So, the blue regions (values less than 1) have warmed less than the global average or cooled, the red ones have warmed more than the average. Fountain: Copernicus satellite datamapped by Ruijian Gou.
The cold bubble and the changing signal of the Gulf Stream are clearly seen in the satellite trend. Note that we are only comparing the pattern, not its amplitude, and the colors correspond to different units: in the observation data we are talking about a moderate change of AMOC, in the model about an almost complete closure. This also explains the differences: on the satellite map the Labrador Sea has not cooled, probably because deep convection still continues. And the Nordic seas have warmed; we have a paper in preparation showing that this is due to the increased flow of warm water into the Nordic seas and probably as a result of the weakening of the AMOC; These two overturning motions are dynamically anticorrelated, but only temporarily until Nordic Sea convection stops.
Together, these two images once again provide clear evidence that a weakening of the AMOC is occurring, as first argued fifteen years ago. Dima and Lohmann (2010). The same fingerprint is also found in a coupled climate model simulation for CO2 doubling conducted by the Geophysical Fluid Dynamics Laboratory at Princeton, as shown in Fig. 1 of this 2018 blog post. And the fingerprint pattern of the cold spot and the Gulf Stream shift can also be seen over a different time interval in the following global image of sea surface temperature change (Fig. 3).
This weakening is particularly worrying because the AMOC has a tipping point, and our recent study has shown that in many of the standard simulations of future global warming carried out for the current IPCC report, the AMOC exceeds that tipping point and dies down in the following decades. He Correctly titled guardian that this danger is “no longer unlikely,” as we had discussed for decades.
Figure 3. Global map of sea surface temperature changes.. Source: ERA5/BBC
What about counterarguments?
I sometimes read arguments against a current AMOC slowdown, but many simply don’t hold up. Let’s take a look at some of them.
For example, increased trade in the Nordic Sea is sometimes seen as contradicting a weakening of AMOC – but that is a non-sequitur since there is no reason why these two circulations should be synchronized, but good physical reasons and empirical evidence suggest that they are, in fact, not correlated.
It is not uncommon for different time periods to be confused, for example when Worthington et al 2021 The reconstruction is cited as questioning a weakening of AMOC. Let’s compare that with the reconstruction of Caesar and others. 2018 where we estimate a weakening of 15% since the end of 19th Century (Fig. 4): I would say that these two reconstructions coincide strongly during the 1981-2016 time interval covered by Worthington.
Figure 4 Various AMOC reconstructions, with RAPID measurements on top. The reconstruction by Frajka-Williams et al. 2015 surface height data used from the satellite, and the Worthington et al 2021 The reconstruction uses a water mass regression based on RAPID data. Graphic: Levke César.
A recent feature article from Terhaar et al. (2025) which has cast doubt on whether the weakening of AMOC covers a longer interval (1958 to 2022). But for the period since 1958, Caesar et al. 2018 also found no statistically significant weakening of the AMOC (so there is no strict contradiction) and what’s more, the calculated input data used (surface heat fluxes) are much more uncertain than the directly measured sea surface temperatures, as we can see from the large differences between their two reconstructions (dark blue and violet) using two different surface flux data sets. And both disagree with Worthington’s probably most reliable method of reconstruction. (More information about Terhaar’s study here.)
Then there is Latif et al. 2022. They do not intend to contradict Caesar’s reconstruction, but they write explicitly that they do not. What they argue is that natural variability is greater than an anthropogenic effect. That is not the same as saying there is no AMOC slowdown. In Caesar’s reconstruction, the multidecadal variability is also greater than the slowing trend. I always show Latif et al 2022 in my talks in support of the observed SST fingerprint pattern indicating a slowdown of AMOC, as their paper shows a clear correlation of SST fingerprint with AMOC (as shown in Fig. 2 here in this post).
Sometimes also an article Rossby et al. 2022 He is cited as questioning an AMOC slowdown. Let’s just quote their summary: “There is evidence of a 2.0 Sv slowdown of the Gulf Stream between 1930 and 2020. Whether and to what extent this reflects a slowdown of the AMOC or the wind-driven circulation cannot be established with certainty. Our estimate of a 0.4 Sv decrease in the AMOC is reported with low confidence.” Therefore, they report a slowdown, albeit with little confidence.
There is also a reconstruction from 1900 by Fraser and Cunningham 2021. They write that “starting in the 1930s we see qualitative agreement with Caesar et al. (2018), with a mostly high AMOC until the 1950s, followed by a weakening throughout the 1960s and then a minor peak around the year 2000.” There is disagreement between 1900 and 1930, where however their method is very uncertain, so they conclude that although their “results do not resolve the weakening of AMOC during the last century, they should not be interpreted as evidence to the contrary.” Which, however, some people do.
As another example, an article by Him and others. 2022 argues, based on a simulation model, that the SST fingerprint pattern could also be caused by surface flows rather than a weakening of the AMOC. However, the observed flows suggest the opposite (prepress).
And finally there was a paper that, according to many outlets, showed a much more resilient AMOC even though it used the same models as other studies and only focused on a wind-driven remnant flow known since the 1990s, and Volkov’s study of a stable Florida current that climate skeptics mistook for the AMOC (see postscript here).
So while there are a large number of studies with different methods using temperature or salinity data or paleoclimate proxy data from ocean sediments that support a weakening of the AMOC since 19th Century (as I’ve discussed before, for example here, here and here), I don’t really see a credible counterargument. If you know of any that I’ve missed, let me know in the comments!
And as a final reminder: if there is a risk that the AMOC is weakening and heading towards a tipping point, we must act accordingly (as with other major risks). This is not a topic that we can afford to wait until we are sure, or pretend that it is just an academic discussion without further consequences.
Correction: I changed the wording with the link about the Baker et al study, as it was pointed out to me that the original was based on a misunderstanding. The study says: “Although simpler models and some global climate models suggest that the AMOC could collapse (i.e., weaken to zero or reverse) under such forcings, it does not collapse in the model experiments considered here.” Many colleagues, including me, understood this as a redefinition of the word “collapse”, as in previous studies, which generally meant a strong weakening (not to zero), even if a shallow wind-driven part remains (as has been known since the 1990s). But Jonathan Baker says this phrase is not intended to be a new definition of “AMOC collapse.” See also my previous article on that study.
If you want more information about this…
My general article in Oceanography magazine (open access, many photos)
My Lecture on the Alfred Wegener Medal at the 2024 European Geosciences Union meeting
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