Talk:Thermohaline circulation

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"The thermohaline circulation is sometimes called the ocean conveyor belt, the great ocean conveyer, the global conveyor belt, or, most commonly, the meridional overturning circulation (often abbreviated as MOC)."

Rahmstorf, S., Thermohaline Ocean Circulation, Encyclopedia of Quaternary Sciences, S. A. Elias Elsevier, Amsterdam 2006.

The MOC is related to the THC but is not the THC. The MOC is at least partially wind driven as opposed to being due to temperature and salinity differences alone.

Conveyor belt is obsolete: Lozier, M. Susan (18 June 2010). "Deconstructing the Conveyor Belt". Science Magazine 328 (5985): 1507–1511. doi:10.1126/science.1189250.  Lfstevens (talk) 23:24, 11 December 2011 (UTC)

  • Conveyor belt is an obsolete and false concept. --Fev 21:45, 6 February 2014 (UTC) — Preceding unsigned comment added by Fev (talkcontribs)

Better Diagram?[edit]

That one was clearly done in MS Paint. Come on, folks. - Darkhawk

This is sourced from an h2g2 article I started writing a while ago, so it needs some work: style, wikification, and gaps filling [also references need page numbers]. It may also be better to split some of this into separate articles e.g. water mass properties. Comments? Tonderai 16:38, 4 Dec 2003 (UTC)

I made a few changes here regarding the wind-vs-density issue. It is increasingly clear that the geometry of the thermohaline circulation (where deep water sinks) is determined by buoyancy, but the rate at which water cycles through this system is determined by mechanical energy supply- though not in a simple way (Ferrari and Wunsch, Ann. Rev. Fluid Mech., 2004; Gnanadesikan et al., J. Climate., 2005).

they are so wrong its not even funny—The preceding unsigned comment was added by User: (talkcontribs).

Effect on Europe?[edit]

I think this [1] pushes the balance too far the other way William M. Connolley 09:45, 20 April 2007 (UTC)

Hi. I think you might mean the previous edit; that one only adds a weblink for the extra reference. Regarding said earlier edit, I was concerned that the study that suggested Europe wasn't warmed by the THC wasn't actually a study; it was a popular review. I wasn't sure if I should {{fact}}-tag it or something for a better reference, so I altered the language instead (it sounded like it was overstating things anyway). This has possibly made things more ambiguous however. The second part of my edit cleared up a chronology problem: the second reference was supposed to be criticising the first, but was actually published before it. I reworded to try to make more sense while retaining the same reference. Anyway, I'm not wedded to the changes at all, but if the text has to revert, I'd prefer a much stronger cite in support of the proposition. It's not really my area of expertise, but I as an oceanographer I routinely hear people describing the THC's northward heat transport as being at least partially responsible for Europe's warmer climate (of course, maybe they're all wrong - I'm no physicist!). Cheers, --Plumbago 10:21, 20 April 2007 (UTC)
OK, I probably meant [2]. But there is a Seager et al paper in QJRMS on the same issue that should be referenced. No need for reverting - its more a matter of needing more tweaking I think. And anyway its not the THC is the North Atlantic Drift William M. Connolley 11:34, 20 April 2007 (UTC)

- It would really cool if there was some information or links to other effects the conveyor belt has on the world, or effects other than on europe its break down would have. Cheers.

And the complete shutdown of the system which is faced by global climate change would be good to include as well.

A cycle slowdown would cause arctic cooling, which would causes increased freezing, which would increase salinity fix the cycle... increasing density... perhaps so far as to speed up the cycle. This feedback can keep the balance. Or it can cause seasonal thrashing with very hot summers and very cold winters every XXX years. These "waves" of hot/cold cycles could also, occasionally, interact and have extreme effects. Call this "thermohaline cycle thrash" (talk) 14:21, 11 January 2010 (UTC)

Cycle duration? (just a few basic calculations)[edit]

1600years cycle duration seems intuitively a bit long, the heat being moved at this rate wouldn't amount to much at all, and any way, with an estimated length of 100,000km the speed would be about 70km/year or less than 1mm/s, which seems intuitively a bit slow.

given a MAX flow rate of 10cm/s, (as i've found quoted elsewhere on-line) then the MIN cycle time is about 30years.

could it be that the 1600years is sort of a misquote, originally intended as a illustration of just how slow the slowest cycle time was, out near the edges of the conveyor where the speed obviously tappers off? —Preceding unsigned comment added by (talk) 21:20, 30 December 2007 (UTC)

100,000 km? William M. Connolley (talk) 22:17, 30 December 2007 (UTC)
earth diameter ~ 12,750km
guess of longest conveyor as between 2 and 3 circumferences
so length between; 76,000km and 115,000km —Preceding unsigned comment added by Asplace (talkcontribs) 17:12, 31 December 2007 (UTC)
i've now found another quote of 3cm/s for flow rates, (fits with the 10cm/s max.) and which just can't be squared with the 0.1cm/s given by the 1600 period.Asplace (talk) 19:36, 12 September 2008 (UTC)
I suspect that the 1600 years comes from the isotopic age of the oldest ocean water (which I've usually heard as 2000 years, but that could just be rough rounding). That is to say that there are parts of the ocean that haven't engaged in gas exchange with the atmosphere for ~2000 years. In that sense, it would represent a maximum time for the motion of water from the surface, to the deep, and back to the surface. Water packets that stay along the primary flow lane probably do cycle much faster than that. Dragons flight (talk) 21:19, 12 September 2008 (UTC)
that sounds much more realistic, and a logical source of the 1600years, so anyone against including this and some clarification on the intro, perhaps with speed readers in mind?
i originally got here having seen the period of the conveyor quoted on TV as the 1600 years value, as if some lazy journo had just read and misunderstood this article. —Preceding unsigned comment added by Asplace (talkcontribs) 20:49, 15 September 2008 (UTC)
Just to clarify, the 'conveyor' schematic is purely that: it illustrates some major oceanic transports, but the arrows usually don't correspond to a clearly delineated flow. Much of the transport is done by turbulent mixing, etc... In the case of THC, there really isn't an identifiable circulation -- it's intrinsically associated with the partly wind-driven meridional overturning. Some of the water may complete a transit over many thousands of years, while some may transit much faster. Other water may find a place at the bottom of the ocean and just stay there for hundreds or thousands of years! —Preceding unsigned comment added by (talk) 00:18, 7 March 2009 (UTC)

Greenland / Agassiz[edit]

Slightly unconvinced by [3]. I have a feeling LA was supposed to be gone by 8.2kyr, but I'm not sure William M. Connolley (talk) 20:51, 28 April 2008 (UTC)

No, remnants of Lake Agassiz / the Laurentide Ice Sheet probably persisted till ~8ka. It's a common hypothesis that the 8.2 ka event was associated with the last major emptying of Agassiz, though its not the only hypothesis for the 8.2 event. Dragons flight (talk) 22:27, 28 April 2008 (UTC)


Shouldn't this be moved to meridional overturning circulation, as that's the more accurate term? Andrewjlockley (talk) 00:41, 31 March 2009 (UTC)

Yes, it should be. It would require a bit of fixes to the language and images as well (to de-emphasize the term thermohaline circulation), but it should definitely be moved. Does anyone object to it being moved? Aleph-seven (talk) 06:30, 18 June 2010 (UTC)
Not if we believe The term thermohaline circulation (THC) refers to the part of the large-scale ocean circulation that is driven by global density gradients created by surface heat and freshwater fluxes William M. Connolley (talk) 08:32, 18 June 2010 (UTC)
I'm with William — the term THC should be preferred both as one that is in common use, and one whose name describes a central aspect of it. --PLUMBAGO 08:44, 18 June 2010 (UTC)
MOC and THC are not the same. The MOC has a wind-driven component whereas the THC is by definition the density-driven part of the circulation. Basically MOC is a geographical descriptor and THC is a process. We should have articles on both, or have a single article that makes the distinction clear. Short Brigade Harvester Boris (talk) 05:11, 22 June 2010 (UTC)
Almost all of this article is about the MOC, not the THC. The first paragraph discusses wind driven circulation, the side diagram shows the global conveyor system (the MOC), etc. I can see an argument for having an article about the THC, but most of this article should be the article about the MOC. Aleph-seven (talk) 08:59, 28 July 2010 (UTC)

I'm agreeing with the people who want the article to be moved to MOC. The article refers to both wind and and thermohaline effects. Also, the first couple of paragraphs could be altered to read better if the title MOC was used. It seems odd to start off with a definition of THC (density driven) and then immediately move on to talk about the importance of the wind. The MOC is a description of the currents that we observe. The circulation is driven by both density differences and wind. The details of these mechanisms are a topic of active research. The article should start off with a physical description and then go on to the driving mechanisms. FMacTavish (talk) 18:59, 22 August 2011 (UTC)

  • Agree. THC should redirect to it. Lfstevens (talk) 20:12, 11 December 2011 (UTC)
  • Agree. The article even says that MOC is the more accurate term. Vaughan Pratt (talk) 16:06, 12 November 2013 (UTC)

Deep Ocean Conveyor Belt Reconsidered[edit]

“This confirms suspicions that have been around since the 1990’s, and likely plays havoc with global models of climate change. The findings by Drs. Amy Bower of Wood’s Hole and Susan Lozier of Duke University et al. are published in a forthcoming issue of Nature.”

[4] —Preceding unsigned comment added by Yayay (talkcontribs) 17:39, 15 May 2009 (UTC)

Um. Its a blog. And it says The implications would be for more cold, oxygenated water along the Mid-Atlantic Ridge, but I’m just making that last part up William M. Connolley (talk) 22:18, 15 May 2009 (UTC)
Maybe correponding Nature article would be more interesting but I don't have access. Nature article YayaY (talk) 02:27, 16 May 2009 (UTC)


A few points seem to be inadequately dealt with. Some may be easy to fix, but some would seem to require expert assistance:

  • History: The piece links to the Younger Dryas, but somehow never uses the phrase "ice age" or mentions the role played by the THC in abrupt climate change. Similarly, the more recent little ice age mentioned in the Shutdown article doesn't seem to be brought up at all here.
  • Deep history: What caused the initial formation of the current cycle? Has anyone studied precusors? Did a similar system arise during earlier periods?
  • Future: Shutdown of thermohaline circulation warrants a brief summary here, and some of the points requested above should be expanded upon there as well.

The current three sentences dropped into the very end of the piece seem out of place and grossly inadequate: Anyone feel comfortable expanding them to answer the questions above? MrZaiustalk 03:57, 11 November 2009 (UTC)

Strangely enough, two hours after I posted this I happened to be watching British Isles: A Natural History, and the third episode says that an older ice age was triggered by a moving THC when the landbridge joining the Americas came into being. Showed a map that had the circulation flowing through a sea where the Isthmus of Panama is now, and then being redirected to the North Atlantic. Where can we find more reasonable, detailed sources discussing that change and others like it?. Would be nice to have a good deal more coverage of changes in the THC. MrZaiustalk 05:35, 11 November 2009 (UTC)

Non-sequiturs and other blunders[edit]


While the bulk of it upwells in the Southern Ocean, the oldest waters (with a transit time of around 1600 years) upwell in the North Pacific... Ummm... Where is the Southern Ocean upwelling documented?

Movement of thermohaline circulation

At the Indian Ocean, some of the cold and salty water from the Atlantic — drawn by the flow of warmer and fresher upper ocean water from the tropical Pacific — causes a vertical exchange of dense, sinking water with lighter water above....
This generates a large but slow flow of warmer and fresher upper ocean water from the tropical Pacific to the Indian Ocean through the Indonesian Archipelago to replace the cold and salty Antarctic Bottom Water. This sentence -- actually the entire third para -- needs a rewrite to bring it into line with the summary image.


Computer models of ocean circulation increasingly place most of the deep upwelling in the Southern Ocean, associated with the strong winds in the open latitudes between South America and Antarctica. Ummm... Where is the Southern Ocean upwelling documented?

All of these are simply not present in the image Thermohaline_Circulation_2. While I do not regard a simple diagram as definitive documentation, the absence of the described features is grounds for suspicion that somebody may have misread the journals used to source the article. (talk) 13:15, 23 April 2011 (UTC)


Is this copied from or the other way around? — Preceding unsigned comment added by Fulldecent (talkcontribs) 13:08, 27 August 2014 (UTC)

Removed the word bullshitting[edit]

The world bullshitting existed instead of shifting on line 61 of the article. I removed it last week anonymously. My change was reverted. I have removed it again. Hopefully a bot will revert my change again ^^. — Preceding unsigned comment added by Valarauca (talkcontribs) 15:44, 2 September 2014 (UTC)