Ancient tree reveals cause of spike in Arctic temperature

Hmmmm……what does everyone think of this? ~ ctm

Here is the abstract:

Contrasting Greenland and Antarctic temperatures during the last glacial period (115,000 to 11,650 years ago) are thought to have been driven by imbalances in the rates of formation of North Atlantic and Antarctic Deep Water (the ‘bipolar seesaw’). Here we exploit a bidecadally resolved 14C data set obtained from New Zealand kauri (Agathis australis) to undertake high-precision alignment of key climate data sets spanning iceberg-rafted debris event Heinrich 3 and Greenland Interstadial (GI) 5.1 in the North Atlantic (~30,400 to 28,400 years ago). We observe no divergence between the kauri and Atlantic marine sediment 14C data sets, implying limited changes in deep water formation. However, a Southern Ocean (Atlantic-sector) iceberg rafted debris event appears to have occurred synchronously with GI-5.1 warming and decreased precipitation over the western equatorial Pacific and Atlantic. An ensemble of transient meltwater simulations shows that Antarctic-sourced salinity anomalies can generate climate changes that are propagated globally via an atmospheric Rossby wave train.

This should be a lot of fun for the technical readers and commenters.  Full paper here.

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51 thoughts on “Ancient tree reveals cause of spike in Arctic temperature

  1. Whatever lags and variations in advances and retreats of ice sheets in the two hemisphere may exist, the fact is that during glaciations, both the Antarctic and Northern Hemispheric ice sheets wax overall and wane at terminations.

    Small remnants of the Inutian North American ice sheet still exist in the Canadian Arctic, while the massive East Antarctic Ice Sheet quit retreating about 3000 years ago.

    • 8 trees I believe. It doesnt take long to be skeptical of your first reaction and read.
      On par with an ice core,
      or a painting of the LIA,
      or a village of vikings in Greenland.
      or grapes in England,

      Another piece in a complex puzzle.

      • Not 8,, they named the dataset “Finlayson 8” see the caption first figure

        Multiple trees of different ages across the late Pleistocene were extracted from a swamp on Finlayson Farm (35° 83′ S, 173°64′ E) in 1998 (refs 31, 32) from which we have identified a 2000-year long kauri log (henceforth ‘Finlayson 8’) to generate a bidecadally resolved 14C series to reconstruct atmospheric radiocarbon content

      • Mosh,

        Not a single tree, but some of various ages at the same site.

        Better than Yamal, and for a different purpose.

      • ” we have identified ‘a’ 2000-year long kauri log”

        ” as recorded by ‘the’ New Zealand tree”

        ‘a’ and ‘the’…………

      • I’m 60 years old. For the last 45 years I have been reading about the most recent hominid fossil find and how it redefines human evolution. It never turns out that way. It is just a snapshot of a moment in time at a single location. Beyond that it is just self-promotion. Sometimes Michael Mann style. Completely unethical b.s.!

  2. From the paper:

    Here we exploit a newly-developed bidecadally resolved 2000-year long atmospheric 14C series obtained from a New Zealand sub-fossil kauri tree (Agathis australis)10 to quantify time scale differences between key records of the last glacial and explore possible mechanisms to explain global climate patterns across this period.

    Yep, it sure sounds like they’re talking about a single tree. Plus, they are also using computer models. What could possibly go wrong?

    • “Multiple trees of different ages across the late Pleistocene were extracted from a swamp on Finlayson Farm (35° 83′ S, 173°64′ E) in 1998 (refs 31, 32) from which we have identified a 2000-year long kauri log (henceforth ‘Finlayson 8’) to generate a bidecadally resolved 14C series to reconstruct atmospheric radiocarbon content”

      sounds like a single tree until you read.

      • sounds like a single tree until you read…..

        “a” and “the”……..

        “a’ New Zealand sub-fossil kauri tree”
        ” we have identified ‘a’ 2000-year long kauri log”
        ” as recorded by ‘the’ New Zealand tree”

      • Kauri seems to be a type of tree, not a statistical method. So a “kauri log” is a single tree. Interesting that a tree has a length measured in years.

      • Steven Mosher on September 23, 2017 at 2:23 pm
        Not 8,, they named the dataset “Finlayson 8” see the caption first figure……

        How did you get this comment in a minute earlier than this comment AND have them say exactly the opposite.

        The comment at 2:24 shows your ignorance.
        The comment at 2:23 shows you understand.

        Did you change timestamps somehow, or did you forget you knew in an instant?

    • They are simply using the Kauri logs to derive sequences of high-precision C-14 ages at 20-year intervals. The biggest “gotchas” are the estimation of the proper beginnings and endings of the C-14 sequences. Unless they can tie to other sequences, the series are “floating” and the start and stop points are best estimates. Using the C-14 and Be-10 – both cosmogenic nuclides – they can estimate new ages on previously studied isotope time series data – again empirical data not “models”. That allows them to then compare empirical data with better age estimations against models – which do not rely on CO2. No “treemometers,” no reliance on CO2 as an explanatory mechanism. They are argue that things are more involved and happen more rapidly than previously argued in the “see-saw” between northern and southern hemispheres. After that, they look at the current models for Pleistocence marine circulation. The only mention of CO2 is in describing the bulk carbon-dating methods description.

    • This is what they are trying to show

      “We observe no divergence between the kauri and Atlantic marine sediment 14C data sets, implying limited changes in deep water formation. ”

      14C and deep water formation.

      right there in words.

      reading and comprehending is the first step.

      once you read an comprehend, then you can attack an argument.

      not with sarcasm, but with better science.

      • Even setting temperature aside, it sounds like a circular reasoning. They used C14 to estimate the age of kauri, and also to estimate the age of the sediment, and – surprise – they are the same!

      • Keep reading oh Mossshhher the once Great and Powerful. You may just discover what the paper is about.

        Unlikely I grant you, but even with your poor reading skills it just might happen.

  3. This reads like an electronically generated paper. Two decades resolution, I don’t think so. How do high salinity anomalies generate Rossby waves? Is this a proxy for evaporation creating salinity highs? Freezing of ice also increases salinity. I’m not going to bother going so far as to read it.

  4. “An ensemble of….simulations…shows that…can…”

    LMFAO

    This is about as far removed from proper science as a packet of crisps is from a Michelin restaurant offering.

    • Yes but it goes on to say that

      “Bayesian age modelling of the radiocarbon inflections and plateaux preserved in the New Zealand kauri against the tropical Atlantic marine Cariaco Basin and Japanese varved Lake Suigetsu (SG062012) records13, 14 (see Methods) places the start of tree growth (and associated changes in atmospheric 14C content) on the timescale of these sequences at 32,250 ± 70 BP and 31,510 ± 80 BP, respectively (Fig. 1).”

      Unfortunately once Bayesian age modelling is introduced into the process then if a hypothesis is extremely unlikely a priori, one should also reject it, even if the evidence does appear to match up.

      The probability of calculating the likelihood of radiocarbon inflections a priori is itself extremely unlikely and so any Bayesian age modelling would be overly self referential and should be rejected from the sample space.

    • Beautiful timber, highly prized for a variety of decorative uses. The logs are isolated from oxidation by being buried in a reducing (swamp) environment.

  5. It is even so.
    Climate debate needs to focus on the deep ocean.
    Deep ocean climate research needs to focus on Antarctica, the “Grand Central Station” of the THC and the place where interglacials begin and end.

  6. Problem is that changes in salinity in the southern hemisphere can often be either a cause or an effect. It is not unusual to see north poll variation in opposition in phase to south pole variation (warm in north, cold in south, and vice versa). When there is a large freezing of southern ocean sea water, there will be significant “brine rejection” from that ice. In fact, during the last glacial it seems a very large pool of very dense, salty cold water pooled in the Pacific off the coast of South America and ocean circulation basically shut down. There is also some evidence that during this time a rather large pool of pure liquid CO2 formed here on the ocean bottom until circulation restarted again.

    Anyway, might be a chicken / egg problem here.

  7. Is a kauri tree a “temperature tree”. I’ve lost track of which trees are immune to the effects of water, bear-poop-fertilizer, shade and everything else but temperature.

    • The trees do not measure temperature directly. They record the 14C content of the air in the annual tree rings. The atmospheric 14C content varies from year to year, decade to decade and century to century. The same variation is seen right around the entire globe. So the 14C curve can be synchronised from site to site, especially given that 14C can be used as a direct dating tool. If temperature is being established from these logs they are using a different proxy to achieve this.

    • Kauri trees grow in New Zealand where the main species is Agathis Australis. New Zealand is in the temperate zone, so the New Zealand kauri species could be deemed to be temperate trees.
      However the genus contains about two dozen species almost all of which are found in the tropics ranging from the Philippines, Borneo, the Indonesian islands, New Guinea, North Queensland, and all the Melanesian islands (where the wonderful Pacific Kauri trees grow (Agathis Macrophylla)).

  8. 

The Bolling-Allerod (Northern hemisphere warming at 14,600 yrs ago) and Younger Dryas (subsequent 1000 yr cold interval) were features of the last deglaciation driven by oceanographic processes. Over the deglaciation starting as early as 22yrs ago the general picture is one of steady changes in Antarctica contrasting with unstable fluctuations in the NH driven by the Atlantic Meridional Overturning Circulation (AMOC).

    The root cause of this is an instability in the AMOC arising from a positive feedback which it possesses. Cold water formation and downwelling in the Norwegian sea drives the gulf stream – reactive flow of Carribean warm and – critically – saline water across the Atlantic to north west Europe. This gulf stream water has high salinity, and this makes the cold water formed in the Norwegian sea even more dense than would result from its temperature alone. So this cold and saline water sinks all the way to the Atlantic floor and is one of the principal drivers of the global thermo haline circulation (THC). This “deep water formation” at the Norwegian sea speeds up the gulf stream – something has to replace all that sinking cold super-salty water. Thus the positive feedback. Where you have a positive feedback in an open dissipative far-from-equilibrium system you have the conditions for nonlinear oscillation. This is directly analogous to the ENSO in the Pacific, the positive feedback of the Bjerknes mechanism (cold upwelling strengthens trade winds strengthening cold upwelling etc.) giving rise to the ENSO nonlinear oscillator, although the AMOC operates over much longer – century and millenial – timescales than ENSO (decadal).


    So a basic oceanographic feature comparing the NH with the SH in the palaeo record is more fluctuation and instability in the NH and more stable, gradual changes in the SH. The nonlinear instability of the AMOC is the root of this. Also, there is a clear signature of interhemispheric bipolar seesawing, whereby when the NH moves in one direction, the SH moves in another. This is not universal however – sometimes at the moments of biggest transition, NH and SH move together.


    About 22 kYa (thousand years ago) Antarctica started warming. The NH at the same time slightly cooled.

    However at about 14 kYa the “Bolling-Allerod” (BA) happened, i.e. the NH abruptly warmed, as evidenced by Greenland cores. This caused a reciprocal pause and slight reversal in the (already long established) gradual Antarctic warming – the bipolar seesaw again. This episode is referred to as the “Antarctic reversal”.

    At the time of the BA there was a sharp rise in global sea level – 20 meters in 500 years. Weaver et al 2003 (link below) show that this was caused by a collapse of the gradually warming Antarctic ice sheet. The pulse of fresh meltwater from Antarctica had the effect of speeding up the AMOC and the gulf stream in the NH, bringing rapid warming to the NH and the BA.

    
The bipolar seesaw continued – as the NH became sharply warmer, there followed in the SH the Antarctic reversal where temperatures went slightly into decline.

    However down in the deep ocean, ongoing century-scale interactions between the SH and NH caused – about a thousand years later – an abrupt stoppage of the AMOC and the gulf stream. In fact the cuplrit was Antarctic Intermediate water (AAIW) – see again Weaver et al. With the interruption of the gulf stream the NH went cold again – the Younger Dryas. In response – by now you get the picture – the Antarctic returned to gradual warming.

    Eventually, after about 1000 years of NH cold with no gulf stream (the YD) the after-effects of the huge Antarctic ice sheet collapse finally subsided allowing the AMOC and the gulf stream to resume. Now followed an exception to the bipolar seesaw – both NH and SH warmed together, around 12 kYa. This marked the final end of the last glacial and the Beginning of the Holocene.


    http://science.sciencemag.org/content/299/5613/1709

    
http://epic.awi.de/15280/1/Lam2004a.pdf

    http://onlinelibrary.wiley.com/doi/10.1029/97GL02658/full
    




  9. As one of the three men who got the Ancient Kauri Kingdom going (by Stewart Bros), I can add some background: We know of trees 1000000 yo buried about 60ft deep IIRC. I soon realised they could be useful for dating. Temperatures? Not so easy. People have only recently clicked to using them for dating, though I think the NZ Forest Research Institute might have some info on that.
    They were subject to changing sea levels and shifting sands which buried them as swamps formed. They are not swamp trees themselves. But they are excellent when fresh, for shipbuilding. So they keep well buried and wet, and gain more beauty from darkening by tannins. Superb for furniture or similar. We are struggling to prevent overseas exploitation of bulk timber right now, after many years of sensible exporting of crafted wood. We three did not gain from this, it was not our aim.

  10. The team who wrote the paper seems to have been led by Chris Turney, an English geographer who is now “Professor of Climate Change and Earth Science at University of New South Wales”
    He has also led a couple of modest expeditions to the Antarctic – one of which came to be known as the “Ship of Fools”.

    • Ah yes, our good friend Chris Turney, he of the Ship of Fools. Explains the incomprehensible jargon, and very dubious nature of this convoluted attempt to discuss ocean circulation as detailed by a 2000-year-LONG log.

  11. A single subject tree ring data set is not an alarming piece. Several now-accepted theories in a variety of research areas have started thusly.

    The location of one of the largest volcanic climate changing explosions was recently identified using this kind of process. http://www.pnas.org/content/110/42/16742.full

    Let’s see where this leads.

  12. By the way, I have finally been convinced of the differences between interglacial/glacial, and interstadial/stadial after a few commenters informed me that I was a bit confused (hell, it’s to be expected well past the first half century of life: to wit I sometimes forget where I put my carry). This link is a standard one I now use to keep my venacular straight.

    http://onlinelibrary.wiley.com/doi/10.1002/2015RG000482/pdf

    • By the way, that link is also a good one to use when talking about replacing destroyed houses built on continental edges, and whether or not to do so on the public dime.

  13. The Kauri tree data only covers 2,000 years – from 25,330 BP to 27,780 BP.

    Considering the uncertainty involved in C14 dating when you go back this far (after 45,000 years, C14 dating uncertainty is so high, it is considered useless so this becomes half useless), there is nothing in this data to support anything about “timing”.

  14. The contrasting temperatures in each hemisphere, during the last ice age, were caused by precession. The precession of the equinox causes a Great Summer in one hemisphere and a Great Winter in the other – simultaneously – the same as a nornal annual year, but the Seasonal Great Year lasts 22,000 years.

    R

  15. The most interesting part of this paper is the straggle to explain a possible quick climatic response to oceans “behavior” without the need of the AMOC slowdown. Especially in regard of the influence of North Atlantic.
    Kinda of “The Day after Tomorrow” scenario but little differently. As some other study(s) previously has tried and many others may keep trying on the same line in times to come.

    From my point of view, it seems to be a way in trying to hide and misinterpret the possibility that actually the North Atlantic happens to be the “canary of climate”, where and when the North Atlantic is more sensitive and more quickly and clearly responds to the climatic trend changes, instead of causing such changes, especially in a TOA negative imbalance period.

    The most hocus pocus in this study is the last part, the conclusions and the hypothetical explanation of the findings, regardless of the research and the analytic method of the data.

    I kinda of like the first part to a degree, which to my understanding shows a high degree of interesting coincidence in the choice period in question. Is like these guys have searched a lot in the data to come up with that actual period, which may hold a similar pattern, to what is happening lately………
    I will be curios to know if this true, did they skip other similar period(s) closer to present, which did not fall under the glacial period! Just wondering…..

    cheers

  16. For those having difficulty interpreting the paper, it’s always worth clicking through to some of the news reports for a simpler explanation (see the ‘more detail’ link on Nature’s webpage) . Scientific papers can be tough to comprehend, even for scientists themselves. This link might help https://www.eurekalert.org/pub_releases/2017-09/uons-atr091117.php

    This paper isn’t particularly making any sort of commentary on the current period of warming. It’s simply saying that their modelling study suggests that freshwater release into the southern ocean from a melting Antarctic ice sheet may have caused warming in the North Atlantic through a series of interconnected oceanic waves during the last glacial period. They say themselves this discovery ‘may’ help inform future projections of climate change. It’s a new potential mechanism discovered and it’s too early to say exactly what it means.

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