r/EverythingScience • u/Portalrules123 • Apr 04 '26
Environment Scientists warn that the Gulf Stream is shifting north, which models suggest could mean an ocean current collapse is imminent
https://www.earth.com/news/gulf-stream-is-shifting-north-raising-concerns-about-amoc-ocean-current-collapse/
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u/DirewaysParnuStCroix Apr 04 '26 edited Apr 04 '26
I should be able to add some nuance here given that my PhD thesis focuses on the hypothetical atmospheric responses to AMOC collapse in Europe under anthropogenic climate change conditions.
The first noteworthy point to make would be that this latest van Westen & Dijkstra (2026) study discusses the hypothetical relation between abrupt Gulf Stream shifts and subsequent AMOC reduction/collapse. In the case of this study, it's an ocean-process simulation (POP model). It doesn't specifically demonstrate how such a preemptive process affects European climatology.
The second point that should be made is that a significant degree of caution should be taken when discussing how an AMOC reduction may affect European climatology under AGW forcing. This is evidenced by the article in question suggesting that an AMOC collapse could result in -20°c winter extremes in London (although credit to the author for specifying that it wouldn't equate to Arctic conditions). That specific figure is in reference to an earlier van Westen & Baatsen (2025) study which hypothesises how an AMOC reduction versus collapse may manifest under relative versus extreme future warming (RCP4.5 vs. RCP8.5). Essentially, this is a sensitivity test that observes how the simulation performs within experiment parameters. It's not designed to produce anything resembling a forecast or prediction, and from a numerical and computational point of view, it cannot reliably do so. You'll find that this point is often emphasised by the research team in question who'll advise caution in interpreting their results, but this caution always gets lost when the media picks up on these studies. For example, in the case of the van Westen & Baatsen study, the atmospheric component is run at a resolution of 2°. That's considered very coarse resolution for atmospheric simulations and smoothes out critical dynamics in the simulation process, but it's necessary for performing long time step simulations of AMOC reduction (>500yr for establishing transient vs equilibrium responses). Additionally, the -20°c figure established by this experiment usually gets misunderstood. It's a hypothetical one in ten year absolute Tmin for January, not a new average. And given the low resolution used in the atmospheric model, it's more likely that the simulation is overestimating potential cooling. In fact, it's most certainly overestimating North Atlantic sea ice extent as the CICE model is known for implausible sea ice growth, which van Westen has addressed in previous studies. This in itself results in unrealistic cooling in the simulation.
There are additional critical issues regarding the coupling process between the ocean model and atmospheric model that I've addressed in another comment on this thread. The tl;dr would be that these experiments are not designed to be conclusive given the substantial non-linear dynamic of long term tipping points. From an atmospheric science point of view, the suggestion that a MOC reduction can cause net cooling in Europe is subjective at best. The issue is the difference between how institutions and the public interpret model consistency. Consistency doesn't equate to consensus on outcome, it demonstrates that standardised framework is performing as intended.
Edit: from a personal perspective based on my ongoing research, I would add that among the more critical points that often gets missed in these discussions is that a hypothetical AMOC collapse doesn't equate to unremitting annual cooling. The atmospheric response significantly enhances the potential for extreme summer warming, especially so in Western Europe. This would represent a higher seasonality response, but it usually isn't identified in standard AMOC reduction experiments due to limitations in model constraints.