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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)[reply]
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.
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.
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)[reply]
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)[reply]
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)[reply]
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)[reply]
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.
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] - Twopapers, 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 threecloseststudies 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)[reply]
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)[reply]
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.)
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)[reply]
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)[reply]