February 11, 2013

Atlantic thermohaline currents nearly stopped in some cold spells of the Ice Age

That is what researchers claim in a new study:

Stephan P. Ritz et al., Estimated strength of the Atlantic overturning circulation during the last deglaciation. Nature Geoscience 2013. Pay per viewLINK [doi:10.1038/ngeo1723]


The Atlantic meridional overturning circulation affects the latitudinal distribution of heat, and is a key component of the climate system. Proxy reconstructions, based on sedimentary 231Pa/230Th ratios and the difference between surface- and deep-water radiocarbon ages, indicate that during the last glacial period, the overturning circulation was reduced during millennial-scale periods of cooling. However, much debate exists over the robustness of these proxies. Here we combine proxy reconstructions of sea surface and air temperatures and a global climate model to quantitatively estimate changes in the strength of the Atlantic meridional overturning circulation during the last glacial period. We find that, relative to the Last Glacial Maximum, the overturning circulation was reduced by approximately 14 Sv during the cold Heinrich event 1. During the Younger Dryas cold event, the overturning circulation was reduced by approximately 12 Sv, relative to the preceding warm interval. These changes are consistent with qualitative estimates of the overturning circulation from sedimentary 231Pa/230Th ratios. In addition, we find that the strength of the overturning circulation during the Last Glacial Maximum and the Holocene epoch are indistinguishable within the uncertainty of the reconstruction.

Summary of thermohaline circulation (public domain, NASA)

In the North Atlantic the best known thermohaline current is the Gulf Stream, which effectively keeps Europe several degrees warmer than it would be otherwise, allowing a relatively dense population at latitudes unheard of elsewhere on Earth. This current was weak at best in the Ice Age. 

Notice that they say that they can find any difference between present day (Holocene epoch) and the Last Glacial Maximum, so it cannot be inferred, it seems, that the glaciation itself had anything to do with the thermohaline currents but only with  some particular cold spells of the late Upper Pleistocene, particularly the HE1 (c. 18-14.6 Ka ago) and the Younger Dryas (c. 10 Ka ago).


  1. Testing what? Should I delete that random message?

  2. Hello, Maju, it's me, argiedude, now that the test went well, I'll get a proper nick as soon as possible.

    I'm making this first post directed to anyone who's interested in helping. I've been reading Glen Gordon's paleoglot website and I have some questions I want to ask him, but his blogspot page for some reason only allows Google accounts, not LiveJournal or other stuff like I'm using. If anyone could forward this question of mine to him, I'd really appreciate it.

    On page 147 ( of "The Ancient Languages of Europe" (Woodard, 2004), it talks about a possible sound change in Proto-Tyrsenic which caused word final vowels to be eliminated. Is the author describing the same phenomenon that you have talked about extensively, and which you've called Cyprian Syncope?

    A second question would be why doesn't you're blog allow LiveJournal or other accounts, like all other blogspot websites do? I'd like to talk to you directly, because I have quite a few more questions.

    PS: I've been following your blog as always, despite not posting now for over a year, which will no longer be the case.


  3. Damn it!

    If anyone wants to help as per my above post, here's Glen's website:


  4. Why didn't you send me an email? You are off topic.

    You can set in the options that only Google accounts can comment. It's way too easy to make one such account, although I guess that not for you (why don't you get another email account and start all over?)

    I'd rather not get involved into acting as intermediary myself, nor honestly I think that you should use other people for such endeavors which are not matters of life and death.

    Otherwise you're welcome back to the world of the living... online.

  5. The Gulf Stream is actually a wind-driven current

  6. The Gulf Stream is actually a wind-driven current


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