Talk:Atlantic meridional overturning circulation

Biogeochemical cycling

The article would benefit from discussion of AMOC in biogeochemical cycling, specifically carbon sequestration. The following sources may be useful: Glacial CO2 cycle as a succession of key physical and biogeochemical processes Glacial greenhouse-gas fluctuations controlled by ocean circulation changes Large-scale distribution of Atlantic nitrogen fixation controlled by iron availability Kdarr (talk) 03:10, 21 October 2017 (UTC)

Figure missing

The figure below describes this variation []. The repetitive cycle obvious in this figure I don't see any such figure.--94.222.124.187 (talk) 18:50, 14 April 2018 (UTC)

Relation to Shutdown of the thermohaline

Some sections of this article should be merged with Shutdown_of_thermohaline_circulation or at least link to it.

done whoever you are Chidgk1 (talk) 12:37, 12 April 2022 (UTC)

Too technical

The article uses a rather good deal of abbreviations, some of which probably make the article harder to read compared to just spelling out what they stand for. Some, such as LSW, aren’t even defined. Furthermore, it suddenly uses the unit “Sv” without ever describing what it is and what it measures. I assume it isn’t referring to Sievert (unit)? Dan Villiom Podlaski Christiansen (talk) 18:23, 27 December 2019 (UTC)

Relation to North Atlantic Current?

Hi, Not an expert at all, but it would be great if anyone could explain in the article the link (or indeed lack thereof) to the North Atlantic Current.

Propose merge Multiple equilibria in the Atlantic meridional overturning circulation

The following discussion is closed. Please do not modify it. Subsequent comments should be made in a new section. A summary of the conclusions reached follows.

To not merge, but rather to keep Multiple equilibria in the Atlantic meridional overturning circulation as a subarticle (too technical for the main page). Klbrain (talk) 05:56, 25 March 2023 (UTC)

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@Deniseruijsch: I propose merging Multiple equilibria in the Atlantic meridional overturning circulation into Atlantic meridional overturning circulation as it is moderate size. Chidgk1 (talk) 12:07, 12 April 2022 (UTC)

Oh wow, one more article on the same (?)/similar topic? Would we need all those equations though, are they relevant for the general public? EMsmile (talk) 13:32, 12 April 2022 (UTC)

They could be put in a footnote as university students might need them. Chidgk1 (talk) 09:32, 13 April 2022 (UTC)

Who would want to check that they are all correct? I wonder if they are all taken from the same publication. It might be better to park them in a sub-article on "Stommel Box Model"? They don't really fit with the prose & encyclopedic style that we use for other articles. Or are such formulas common in other articles that I haven't looked at yet, perhaps the mathematical or electrical engineering ones.EMsmile (talk) 10:34, 13 April 2022 (UTC)

I have been rewriting this article recently, and I would agree with turning that article into a Stommel Box Model article instead, as nearly all of its non-repeated content is about that model type. The only part of this article where the information from "Multiple equilibria" page would fit is in/around the AMOC stability section, and it is already quite long. Moreover, with some recent research questioning the accuracy of standard SBMs, spending so much time on their mechanics in this (already long) article is unlikely to be appropriate. InformationToKnowledge (talk) 11:40, 4 October 2022 (UTC)

Having looked at the equilibria article (and having written most of this one), I think the topic of AMOC stability and multiple equilibria is easily worthy of its own article. But I do agree that that box model section is too hardcore, and the article would benefit from a bit of focus and improvements. I'll take a look, and alert some area-experts to its presence and need for improvement. Robbie Mallett (talk) 13:30, 16 October 2022 (UTC)

I've changed a bit how the topic "Multiple equilibria in the Atlantic meridional overturning circulation" appears in this article and would now argue that a merger is not suitable. This is because the content at Multiple equilibria in the Atlantic meridional overturning circulation is very detailed and specialised, and probably useful but better off as a sub-article, not merged into the main article. EMsmile (talk) 12:39, 24 October 2022 (UTC)

The discussion above is closed. Please do not modify it. Subsequent comments should be made on the appropriate discussion page. No further edits should be made to this discussion.

• Question Is the potential merge still in the air, or have the re-writes taken that suggestion off the table? Joyous! Noise! 04:51, 13 March 2023 (UTC)

My opinion (see 24 Oct 2022 entry above) is that a merger is no longer suitable. EMsmile (talk) 11:28, 13 March 2023 (UTC)

"Potential effects: anoxia and euxinia"

This section is unusually speculative, especially when compared to the rest of the article. After I spent quite some time to ensure that all scientific citations have up-to-date links, I was able to look at the 7 citations cited there, and frankly, all of them are only vaguely related to the rest of the article.

Light penetrates only about 100 meters to 200 meters of the ocean top layer.[80] - Reference "How far does light travel in the ocean?" Reliable, self-explanatory reference, which mentions nothing about the subject of this article.

Since light is required for photosynthesis to take place, oxygen production by phytoplankton can occur only at this level. The thermohaline cycle causes mixing of the deep ocean water (that would be oxygen-free) with the oxygen-rich water from the surface. [81] - Reference The Ocean Takes a Deep Breath (Interestingly, that paper is 18 years old, yet appears not to have been cited in any other literature.) It does mention that "Deep convection is the major mechanism for replenishing oxygen in the deep interior of the world ocean, and its variability affects the use of atmospheric oxygen to monitor the global carbon cycle."

Thus, the thermohaline cycle brings oxygen into the deep layers of the ocean and allows marine life to breathe, and degradation to happen aerobically. If the thermohaline cycle shut down, it has been proposed that the marine life dies off and sinks to the ocean ground. It has been established that climate change is responsible for the loss of oxygen in the ocean, both because oxygen dissolves worse in warm water, and because of weakening thermohaline circulations.[82] - Reference Declining oxygen in the global ocean and coastal waters only appears to provide explicit support for the final sentence. "it has been proposed that the marine life dies off and sinks to the ocean ground" - proposed by whom? Certainly not by any of the citations used in the article. Never mind that it should say "ocean floor" instead of ocean ground, but that is the least of this paragraph's problems.

With too little oxygen, anaerobic digestion through bacteria would create methane and hydrogen sulfide from the biomass. [83][84] - Two papers, both over 15 years old. Notably, both are focused on the deep past, and appear to have nothing to say about either the AMOC or the recent climate change.

The toxic hydrogen sulfide gas could then, when the ocean contains too much, get released into the atmosphere in a so called chemocline upward excursion.[83] Hydrogen sulfide poisoning of the atmosphere is one of the potential causes that might have led to the Permian-Triassic extinction event.' [85][84] [86][citation needed] - The section ends here. The final two new references are another 16-year old study (which at least does mention "a stagnate global ocean circulation in concert with paleodata indicating low oxygen levels at ocean depth" in its abstract) and a book from 2008.

All in all, there is only one post-2010 reference in this section, and no references which appear to draw an explicit link between the shutdown of the AMOC in the present or future climate and a chemocline upward excursion. I tried to look up any more recent studies myself, but the three closest studies are still very far from what this section currently implies. Moreover, one 2015 study appears to suggest that the AMOC collapse would actually increase oxygen concentrations in the ocean interior.

The reduction in the export production decreases the biological O2 utilization below the subsurface waters (Figure 4c), leading to oxygen increase in the ocean interior. The enhanced remineralization rate due to seawater warming also decreases O2 utilization in the deep water because of decreased transfer efficiency of organic matter to the deep water. Consequently, the global mean O2 increases by ~35 µmol/L in the deep ocean (below 1000 m; see Figure 5b). The biological effect in the deep ocean is marked in the tropical oceans where the present export production is larger (Figure 6b), which is consistent with the findings of a previous study [Matear and Hirst, 2003]. The reduced biological O2 utilization accumulates in proportion to the ventilation time. Therefore, in the deep North Pacific and tropical deep oceans, the biological effects become the dominant mechanism of oxygen recovery: a more than 40 µmol/L increase of oxygen concentration is found. Biological effects play a greater oxygen-enhancing role in the 4 × CO2 experiment than in the 2 × CO2 experiment (Figure 5), because the AMOC collapse in the 4 × CO2 experiment would decrease the export production and hence increase the oxygen concentration. Schmittner et al. [2007], who derived the AMOC collapse from freshwater input, similarly ascribed the increase in thermocline oxygen concentrations to reduce export production.

So, what do we do with this section as it stands? Does it make sense to update it, or should we just remove it entirely, and only add the few relevant references above to the other sections of this article? InformationToKnowledge (talk) 15:31, 4 October 2022 (UTC)

Since nobody had objected in over 10 days, I went ahead with removing the section and using more relevant references in the "Impacts of slowdown" section instead. InformationToKnowledge (talk) 22:51, 14 October 2022 (UTC)

Thanks! You seem to really know what you are doing and have spent a lot of time on this! I didn't check all of your changes (AMOC is not my area of expertise) but I feel I can rely on your judgement calls on this. So thank you! I've just made some small adjustments to the structure, moving some headings around. Hope you agree with those, if not then let's discuss. EMsmile (talk) 12:52, 24 October 2022 (UTC)

I think that those adjustments were very successful overall! I felt that I ended up with too many sub-sections after my previous revision, but I didn't quite know what to do about that, and your edits resolve it nicely. (The main thing I disagreed with was that "Further" link to the tipping points article, since it's really not needed here.)

Hope you like the latest revisions to lead section, and if so, we can go on to finally remove that tag. InformationToKnowledge (talk) 01:10, 28 October 2022 (UTC)

Thanks. I think the lead is actually still too short. It should be a good summary, be about 4 paragraphs long or 450 to 600 words. Currently it's only 371 words. A longer lead is better because many readers will only read the lead, nothing else. Voice assistants often read out the first sentence from the lead by the way (I tested this recently with Amazon's Alexa by asking "what are the effects of climate change on oceans?". I was chuffed that Alexa read from our Wikipedia article! This is just to say that the leads are so important). EMsmile (talk) 11:09, 28 October 2022 (UTC)

Ensuring minimal overlap with thermohaline circulation

When I first started to look at this topic, I had a moment of confusion how AMOC and thermohaline circulation are related. I've also written on the talk page there. I got advice by Tim Jickells (I'm working with him currently on effects of climate change on oceans). He wrote: "It seems like both terms are used almost interchangeably, even though the A in AMOC refers to the Atlantic. The UK Met Office climate change pages refer to AMOC, but perhaps they inevitably focus on the Atlantic particularly. I see there are wikis on both terms and they do seem to cross link the two terms, so I think generally using a phrase like “the Atlantic Meridional Ocerturning circulation (AMOC) which is part of a global thermoholine circulation (THC)” somewhere in the text is the simplest way to handle this." I think this is useful (I have added this sentence in both articles now). We should also ensure both articles do not overlap more than necessary. E.g. the whole topic of shutdown should be bundled here, not at thermohaline circulation, since shutting down the AMOC would also shut down the thermohaline circulation. There might be other areas in both articles where we could streamline the content better to avoid overlap (and hence avoid additional work for editors when updating content). EMsmile (talk) 12:42, 24 October 2022 (UTC)

Update: I think this has now been achieved quite well, as there is an excerpt at thermohaline circulation that links to the section on shutdown in the AMOC article. EMsmile (talk) 09:21, 6 July 2023 (UTC)

Several points that need elaboration/clarification for a layman like me

1. "zonally integrated" are mentioned twice in this article, can anybody help explain what they are? 2. Can we have a plain and simplified caption for "File:95307main fig4m.jpg?" I just can't understand the file by reading the current caption. 3. Can we have more detailed interpretation for "File:Worthington 2021 RAPID". Thanks in advance for the assistance. ThomasYehYeh (talk) 09:05, 20 November 2023 (UTC)

I am also not sure about these points. Have you tried reaching out to an expert on oceans? Perhaps someone is willing to help, I've had luck in the past with Tim Jickells. EMsmile (talk) 19:44, 15 December 2023 (UTC)

User:InformationToKnowledge, are you able to help with these clarifications? I also stumbled over "zonally integrated" today. EMsmile (talk) 12:39, 8 March 2024 (UTC)

@EMsmile All of these points should be addressed by now. "Zonally integrated" doesn't really describe anything complicated - it's mainly a reference to its three-dimensional structure with different layers of ocean water involved, basically - but it is clearly not approachable language, so I removed it, as it didn't add anything anyway. The captions should be improved a lot now as well.

@ThomasYehYeh I am guessing you asked these questions because you were trying to translate this article, right? (I have seen your work translating my effects of climate change on livestock article - many thanks for that!) If so, I only hope you have not spent too much time on it at the time, because, well, I ended up rewriting practically all of it now. Massive improvements have been made: even Kevin Trenberth, whose advice I requested and acted upon for parts of the article, such as the overall structure, says it's better now.

After these improvements, I doubt that this article change much more in the foreseeable future. However, we can only be sure about it once this article gets reviewed and accepted for GA, which is hopefully not far off now. InformationToKnowledge (talk) 20:17, 14 April 2024 (UTC)

Gulf Stream says AMOC shutdown won’t make Britain a lot colder

Doug Weller talk 20:15, 18 January 2024 (UTC)

@Doug Weller Where? Can you point me to the sentence in that article which specifically says that? And more importantly, this article has multiple peer-reviewed references which specifically say that Britain would become colder, including some from 2020 and this year. InformationToKnowledge (talk) 20:24, 14 April 2024 (UTC)

I don’t know what the article said when I read it, but now it says “ A noticeable effect of the Gulf Stream and the strong westerly winds on Europe occurs along the Norwegian coast. Northern parts of Norway lie close to the Arctic zone, most of which is covered with ice and snow in winter. However, almost all of Norway's coast remains free of ice and snow throughout the year. The warming effect provided by the Gulf Stream has allowed fairly large settlements to be developed and maintained on the coast of Northern Norway, including Tromsø, the third-largest city north of the Arctic Circle. Weather systems warmed by the Gulf Stream drift into Northern Europe, also warming the climate behind the Scandinavian mountains.” Doug Weller talk 20:37, 14 April 2024 (UTC)

New paper that says "AMOC is on tipping course"

there is new research that says "AMOC is on tipping course", but I don't know the quality of the research as I am not an academic so I am uncomfortable adding it to the projections section, would be cool if someone with knowledge could add it if it's deemed of good quality https://www.science.org/doi/10.1126/sciadv.adk1189 https://www.realclimate.org/index.php/archives/2024/02/new-study-suggests-the-atlantic-overturning-circulation-amoc-is-on-tipping-course/ Abortthieu (talk) 23:58, 12 February 2024 (UTC)

I agree with you, this needs to be looked at. I also saw it all over the news and was surprised by it (I thought the near-term) tipping risk was regarded as low). So I am unsure on what to do but am hoping that someone who understands AMOC better can decide if and how to add content from that paper? Check out the spike in pageviews for the AMOC article recently here. EMsmile (talk) 09:08, 1 March 2024 (UTC)

@Abortthieu@EMsmile I saw this paper around the same time, but I found it difficult to integrate without making a lot of other changes to the article. It is now present in the newly created "Modelling AMOC collapse" section, since it does not really make a concrete projection, but rather presents a modelling experiment which shows a collapse under intentionally artificial conditions. Explaining the structure of the experiment and its limitations had been more difficult than the usual, but this reference helped a lot. InformationToKnowledge (talk) 20:04, 14 April 2024 (UTC)

Questions about last paragraph in the lead

I have two questions about the last paragraph in the lead (pinging User:InformationToKnowledge as I think you worked on this last):

1. Is that para going into too much detail ("one study says this, another says that, but another one says that..."). Can we either summarise this better ("there is ongoing debate about XXX"?) or stop after this sentence and move the rest to the main text?: Earth system models used in the Coupled Model Intercomparison Project indicate that a collapse is only likely after high levels of warming are sustained well after the year 2100.
2. Why are there so many refs in the lead that are unique to the lead and not used in the main text? To me this hints at a situation where the lead contains unique content, rather than summarising content that is also in the main text? Surely as a rule of thumb each ref that is used in the lead should be used at least twice in the article overall: once in the lead and once (or more) in the main text? EMsmile (talk) 12:42, 8 March 2024 (UTC)

The second issue was because I added those refs in preparation for using them to cite additional information in the main text afterwards. However, this article turned out to require a much larger rewrite than I anticipated at first, which is why the issue persisted. The rewrite should finally be effectively done by now, and this issue should not be present now. I think I have sufficiently condensed the lead to deal with the first issue as well. InformationToKnowledge (talk) 19:54, 14 April 2024 (UTC)

Relevant citations

Some related citations to add. I haven't added them as I'm still a new member here and don't want to overstep any boundaries too soon. All of these publications either directly or indirectly reference AMOC variability and the implications for maritime European seasonality;-

• European summer weather linked to North Atlantic freshwater anomalies in preceding years (Oltmanns et al. 2024)
• Drivers of exceptionally cold North Atlantic Ocean temperatures and their link to the 2015 European heat wave (Duchez et al. 2016)
• Accelerated western European heatwave trends linked to more-persistent double jets over Eurasia (Rousi et al. 2022)
• Uncertainties in the Arctic Ocean response to CO2: a process-based analysis (Saenko et al, 2023)

Proxy-based analogs;-

• Interstadial Rise and Younger Dryas Demise of Scotland's Ice Fields (Bromley et al. 2018)
• Warm summers during the Younger Dryas cold reversal (Schenk et al. 2018)

Supplementaries;-

• Evidence for massive methane hydrate destabilization during the penultimate interglacial warming (Weldeab et al. 2022)
• Ocean versus atmosphere control on western European wintertime temperature variability (Yamamoto et al, 2015)
• The variable European Little Ice Age (Wanner et al. 2022)

Some of these publications may already be referenced in the article but I've not noticed them. Apologies for formatting, still figuring out how to format on mobile. There are plenty more similarly related publication if anyone deems them relevant enough to add. Carcajeux (talk) 17:20, 31 May 2024 (UTC)

@Carcajeux Thanks for both taking an effort to do this, and for taking a careful approach to a developed article! At a glance, practically all of those papers would be useful somewhere in this wiki (second-to-last reference is an exception, as its Lagrangian approach tends to be less reliable than the alternatives, and it doesn't appear to have been particularly influential in 9 years since publication), but I am not sure how many of them would be useful in here specifically.

As you can see, this article is already fairly long, so we should be careful about which research (especially primary research) deserves to be included here, and which is a better fit for a smaller yet more focused article. I'll still be looking at every paper in more detail over the next few days, and if no-one else does anything first, I'll get back to you once I have made my decision on all of them. InformationToKnowledge (talk) 17:41, 1 June 2024 (UTC)

Section on paper by Peter and Susanne Ditlevsen

Someone added on the talk page that this Wikipedia article was mentioned in the media. I followed the link which took me to this: https://archive.is/2024.08.04-225705/https://www.wired.com/story/amoc-collapse-atlantic-ocean/#selection-1397.525-1397.532 . And then to this: https://en.wikipedia.org/wiki/User_talk:Pditlev . It's a shame that User:Pditlev got blocked over this, rather than having a conversation together. I had a look at the paragraph in question and wonder if everything has been worded correctly now. It's about this edit which got reverted back in February.

The current wording is now: "In 2023, a statistical analysis of output from multiple intermediate-complexity models suggested an AMOC collapse would most likely happen around 2057 with 95% confidence of a collapse between 2025 and 2095. This study received a lot of attention and criticism because intermediate-complexity models are considered less reliable in general and may confuse a major slowing of the circulation with its complete collapse. The study relied on proxy temperature data from the Northern Subpolar Gyre region, which other scientists do not consider representative of the entire circulation, believing it may be subject to a separate tipping point. Some scientists have described this research as "worrisome" and noted it can provide a "valuable contribution" once better observational data is available but there was widespread agreement among experts the paper's proxy record was "insufficient". Some experts said the study used old observational data from five ship surveys that "has long been discredited" by the lack of major weakening seen in direct observations since 2004, "including in the reference they cite for it"."

Is there anything that should be modified based on what Pditlev said? For me it sounds OK although I wonder if it isn't overly detailed given that it's only about one particular study. Should be condensed a bit? Pinging User:InformationToKnowledge EMsmile (talk) 06:47, 16 August 2024 (UTC)

References

EMsmile (talk) 06:47, 16 August 2024 (UTC)