I have been receiving many media consultations about a New document about the AMOC (Circulation of southern Atlantic dump), which has just been published. In my opinion, this great interest in the media is perhaps due to the confusing messages transmitted in the title of the document and in the press releases in this regard by Nature magazine and the MET office. Whether or not, these give the impression that the new results results suggest that AMOC is more resistant than previously thought. That (unfortunately!) It is not the case.
This new article does not (and does not affirm) contradicts previous modeling studies on future AMOC changes and its climate impact, as one of the authors (Richard Wood) has confirmed (we are currently attending an AMOC workshop in Utrecht). They are the same models, which show the same things, only the writing is different. What the previous studies have described an ‘Menoc collapse’ is now called ‘no collapse’. It is essentially a discussion about semantics, not physical. Do you call it an amoc collapse if a weak and shallow dump driven by the wind persists after the thermhaline part has collapsed? Or not?
That is not any difference in climate impact. The climate impact of AMOC on these simulations of models is the same as in previous studies, which in fact have used the same models and, in fact, in fact the same model experiments, since this study has analyzed the executions of existing models.
A typical example of them is the document of Bellomo et al. 2023 Using the EC-Arth3 model, that same model is also included in the new article by Baker et al. If you try to kill the AMOC adding a lot of fresh water to the North Atlantic (without increase in greenhouse gases), it obtains the following change in the volume of the Atlantic (Fig. 1).
It is clear that, as usual, there is some remains. The climatic impact resembles other models (Figure 2): Mass cooling in the northern hemisphere.
Figure 2 Surface temperature change in response to a nearby point of the AMOC.
Another example is the analysis of the results of CMIP6 that I showed in me Presentation last October in the assembly of the Arctic Circle, when presenting the open letter by 44 experts in the Council of Nordic Ministers. He Preimpression This work has been online since last September. CMIP6 is the generation of current model, also used in Baker et al.
It presents a selection of standard climatic scenarios with these CMIP6 models, as shown in the latest IPCC report, in which the AMOC stops largely in the next century, as shown in Figure 3.
Figure 3 AMOC FORCE AND TRANSPORT OF OCEANIC HEAT AT 26 ° N in a selection of CMIP6 models in which the amoc almost collapses.
It is clear that some dump remains remain in all of them, as expected, since it is the part driven by the density (that is, thermohalin) of the AMOC that has a well -known turning point, due to the famous feedback of transportation of Salt of Stommel (1961). It has been well established since the 1990s (Toggweiler and Samuels 1995) That the AMOC also has a component driven by the winds, which will persist provided that the winds will not stop blowing (except possibly if it changes to the North Pacific instead of the North Atlantic). Actually, we point out in our predimpression mentioned above that we focus on whether “the deepest thermohaline part of the AMOC is weakened and/or collapse, since it is only this part of the AMOC that has a turning point.” Now the new article focuses on the wind driven, which thus complements our study, but in no way contradicts it.
Does not change the risk assessment and the impact of future AMOC changes in response to global warming caused by humans.
(Publish a link in the comments if you see the coverage of the media of the Baker study).
Script publication: As apart, together with my Australian colleague, Matt England, I published a systematic system Study on the wind driven of the AMOC already in 1997.
#media #inform #AMOC #study
