From the University of Massachusetts at Amherst
AMHERST, Mass. – For more than 30 years, climate scientists have debated whether flood waters from melting of the enormous Laurentide Ice Sheet, which ushered in the last major cold episode on Earth about 12,900 years ago, flowed northwest into the Arctic first, or east via the Gulf of St. Lawrence, to weaken ocean thermohaline circulation and have a frigid effect on global climate.
Now University of Massachusetts Amherst geoscientist Alan Condron, with Peter Winsor at the University of Alaska, using new, high-resolution global ocean circulation models, report the first conclusive evidence that this flood must have flowed north into the Arctic first down the Mackenzie River valley. They also show that if it had flowed east into the St. Lawrence River valley, Earth’s climate would have remained relatively unchanged.
“This episode was the last time the Earth underwent a major cooling, so understanding exactly what caused it is very important for understanding how our modern-day climate might change in the future,” says Condron of UMass Amherst’s Climate System Research Center. Findings appear in the current issue of Proceedings of the National Academy of Sciences.
Events leading up to the sharp climate-cooling period known as the Younger Dryas, or more familiarly as the “Big Freeze,” unfolded after glacial Lake Agassiz, at the southern edge of the Laurentide ice sheet covering Hudson Bay and much of the Canadian Arctic, catastrophically broke through an ice dam and rapidly dumped thousands of cubic kilometers of fresh water into the ocean.
This massive influx of frigid fresh water injected over the surface of the ocean is assumed to have halted the sinking of very dense, saltier, colder water in the North Atlantic that drives the large-scale ocean circulation, the thermohaline circulation, that transports heat to Europe and North America. The weakening of this circulation caused by the flood resulted in the dramatic cooling of North America and Europe.
Using their high resolution, global, ocean-ice circulation model that is 10 to 20 times more powerful than previously attainable, Condron and Winsor compared how meltwater from the two different drainage outlets was delivered to the sinking regions in the North Atlantic. They found the original hypothesis proposed in 1989 by Wally Broecker of Columbia University suggesting that Lake Aggasiz drained into the North Atlantic down the St. Lawrence River would have weakened the thermohaline circulation by less than 15 percent.
Condron and Winsor say this level of weakening is unlikely to have accounted for the 1,000-year cold climate event that followed the meltwater flood. Meltwater from the St. Lawrence River actually ends up almost 1,900 miles (3,000 km) south of the deep water formation regions, too far south to have any significant impact on the sinking of surface waters, which explains why the impact on the thermohaline circulation is so minor.
By contrast, Condron and Winsor’s model shows that when the meltwater first drains into the Arctic Ocean, narrow coastal boundary currents can efficiently deliver it to the deep water formation regions of the sub-polar north Atlantic, weakening the thermohaline circulation by more than 30 percent. They conclude that this scenario, showing meltwater discharged first into the Arctic rather than down the St. Lawrence valley, is “more likely to have triggered the Younger Dryas cooling.”
Condron and Windor’s model runs on one of the world’s top supercomputers at the National Energy Research Science Computing Center in Berkeley, Calif. The authors say, “With this higher resolution modeling, our ability to capture narrow ocean currents dramatically improves our understanding of where the fresh water may be going.”
Condron adds, “The results we obtain are only possible by using a much higher computational power available with faster computers. Older models weren’t powerful enough to model the different pathways because they contained too few data points to capture smaller-scale, faster-moving coastal currents.”
“Our results are particularly relevant for how we model the melting of the Greenland and Antarctic Ice sheets now and in the future. “It is apparent from our results that climate scientists are artificially introducing fresh water into their models over large parts of the ocean that freshwater would never have reached. In addition, our work points to the Arctic as a primary trigger for climate change. This is especially relevant considering the rapid changes that have been occurring in this region in the last 10 years.”
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Conclusive evidence that the warmists continue to go to any length to push their fantasy agenda in the face of reality.
@ur momisugly James Cross 5:16
“A comet crashing into the ice sheets would have vaporized an enormous amount of water which could have fallen as snow over North America, Siberia, Northern Europe, and the the Arctic itself, increasing significantly the Earth’s albedo and affecting the ocean circulation too.”
Great theory–now if you can weasel your way into access to a supercomputer you can PROVE it CONCLUSIVELY, all from the comfort of your own office!
“Conclusive evidence is, well, evidence that is conclusive,at least in the eyes of the beholder.
The evidence can be in any format : computer modelling that is based on very persuasive
assumptions and is driven by persuasive logic.
Conclusive evidence? What evidence? Get a mini sub up there and dig up rocks that shouldn’t be in the Arctic basin. Been done in other areas on the globe. The Montana area all the way down through Oregon’s Willamette Valley is strewn with boulders that geologically speaking, didn’t just grow there. Climate scientists who worship at the feet of their super duper rad computer haven’t a clue.
I believe Bill Illis is saying water flows downhill. If true, does that not contradict this “conclusive evidence”?
Sadly, the state of “science” is do a computer rendition based on your guess and voila, it proves it. Now you write a paper declaring it because everyone knows that “supercomputers” are smarter then men, right?
By the way, I disagree with the concept that they could only get their “high resolution model” because of the speed of a super computer. Unless there are idiocyncracies in the programming language for the super computer that can’t run on slower machines, then the same “resolution” was possible on slower machines, but it would have taken longer. It sounds like “programming hype” to me. Models are models of what someone “believes” to be the situation being analyzed, not necessarily the actual situation.
“Now University of Massachusetts Amherst geoscientist Alan Condron, with Peter Winsor at the University of Alaska, using new, high-resolution global ocean circulation models, report the first conclusive evidence that this flood must have flowed north into the Arctic first down the Mackenzie River valley.”
I’m an accountant, not a scientist. But in my profession, computer models don’t provide conclusive evidence of anything.
Keep up your excellent posts, rgb. There is actually a physical mechanism that could be used to simulate the authors’ conclusions; however, it might be quite expensive in that a physical model would need to be constructed in one of the nation’s water flow simulation tanks, a very detailed labor intensive undertaking, but it could be done.
AngusPangus says:
With no qualitative facts to support…
But in fact they have no support at all except to say that they have a bigger, better, quicker, slicker computer. This is science by children, or if they are not children, then an alternative explanation is that they put forth their super-model cum super-computer in the hope of hooking some super-funding. This critique does not sound nice, does it? But unfortunately, it is the age we live in and these corrupting influences need to be addressed, and climate modelers are among the worst offenders.
Re: cause of the Younger Dryas
Only factor where ocean currents could (but not necessarily ) cause glaciation in the far North Atlantic is some kind of temporary blockage in the Faroe Bank Channel, depriving the Arctic ocean of part of warm water inflow.
Faroe Bank is about 450m high, 200km long and only 50km wide.
The bathymetry of the Faroe Bank Channel
http://www.vukcevic.talktalk.net/FBC.gif
http://www.vukcevic.talktalk.net/G-Sr.gif
revels its very unusual shape, a clear obstacle to large volume of the Atlantic warm water inflow into the Arctic ocean. This is geologically active area, so sudden blockage (by soft volcanic tephra) and subsequent erosion would explain short duration of the Younger Dryas of only 1.3 k year.
Alternatively by removing section of the Faroe Bank (outlined in the red) would increase warm waters inflow, which could be sufficient to prevent the all year around Arctic Ocean freezing, necessary for the onset of any future glaciation.
Oh yeah!
I once built a computer model for my retirement fund. First I was earning 5% a year. After a few years, I redid the model and lowered the yearly earnings to 3% which was actual at the time.
Then the economy did the nose dive and that model was useless. Worse than useless as some of those steady earning blue chip stocks either went bust or darn near.
And I thought the model based on my actual yearly earnings was pretty darn good too.
So let’s see if I understand the model proposed in the above paper…
They believe in the meltwater scenario for causing the warming reversal back into a freeze.
So they built a model.
They refined the model, ran it on fancy equipment and in their minds. This model is now proof?
Har! Har! Har!!! What a bunch of religious zealot one track nerds!
What I’d like to see in this ‘proof’ process of a theory is the verification that cold fresh water will ride on top of the gulf stream and prevent; heat transfer, cooling and sinking of the dense salty water.
Giving how rapidly heat wants to rise and ‘conduct’ in water. I find the whole belief process for a cold water trigger for climate deep freeze darn loose. If the water is fresh enough so that it floats AND it is released north, it then freezes and floats wherever artic ice is blown. If it drains on top of a moving truly massive warm river of gulf water, then it is pushed north while getting warmer until it freezes and gets blown by artic winds. Just how different is fresh water versus frozen low salt ice?
More powerful computers do not produce better results. Given the same unverified data and the same unverified code, they just give the same crappy results faster.
rgbatduke says:
November 6, 2012 at 5:04 am
“. . . that last millions of years . . .
“. . . this AND this AND that, not just . . . ”
In the timeframe suggested, additional “ANDs” come into play. The closing of the Isthmus of Panama being one:
How the Isthmus of Panama Put Ice in the Arctic
Drifting continents open and close gateways between oceans and shift Earth’s climate
http://www.whoi.edu/cms/files/dfino/2005/4/v42n2-haug_2272.pdf
This might also be of interest:
http://motls.blogspot.com/2010/07/in-defense-of-milankovitch-by-gerard.html
. . . follow the link to Gerard Roe’s paper.
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Some more “ANDs”:
The ice-margin lakes drained through various outlets in North America. Not mentioned in the post or comments was the Mohawk/Hudson and the now drowned canyon of that outflow. Interior passages (to the Mississippi) include the Little Miami (to the Ohio, at Cincy) and the Wabash (both receiving water from Lake Maumee (~~L. Erie), the Chicago R. drainage of lake water, and the Allegheny River (western PA & NY) marking the edge of the ice lobe in this region. Then there is the Missouri R. with its now shortened northern tributaries (isostatic rebound to the north). And, in the west, melt-water flowed catastrophically from Montana via the Columbia R. drainage.
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. . .their high resolution, global, ocean-ice circulation model that is 10 to 20 times more powerful than previously attainable, . . .” [from the paper]
The above makes me think of several Richard Feynman quotations.
This is not a “study”, but rather a conjecture based upon a computer model subject to GIGO like all computer models and proves nothing. If it had a face it would look like a bucket of snot.
“..Now University of Massachusetts Amherst geoscientist Alan Condron, with Peter Winsor at the University of Alaska, using new, high-resolution global ocean circulation models, report the first conclusive evidence that this flood must have flowed north into the Arctic first down the Mackenzie River valley.”
I hate to nit-pick but what they offered wasn’t evidence but conjecture. That is, unless computer simulations are now considered evidence. I understand where the scientists are coming from, but computer modeling isn’t the same as say soil or ice core samples. Evidence usually refers to hard physical things that can be measured and evaluated.
Out of curiosity, is there any guess or information about the change in Ocean PH because of this event?
I’m curious because I would expect a sudden and drastic change causing the immediately affected area to become more neutral, not unlike the current PH change.
And so this is how the era of giantism in climate computers began. Each new model and computational effort was superior to any that came before it and more and greater resources were fed into the rapidly evolving beast with natural advantages over the smaller, inferior types. This trend continued for eons and without regard to the tradeoffs, costs of operation, and absurdities involved. The bigger the better until the blunt truth fell from the sky and wiped the previous trend from the face of the earth.
Looking for something that causes mammoths to freeze with fresh flowers in their stomachs… using Occam’s Razor, the simplest way I can imagine this is by the notion of a pole shift, say if the North Pole had centred on the Laurentide ice sheet but suddenly shifted to its present position, due to a “fly-past”.
I say “sudden” but if we have another object in space doing the pulling, it would be gradual enough not to be felt as total seismic shocks though it might cause… changing sea levels in some places, as the Earth’s new polar flattening settled in… and perhaps some of the atmosphere is being dragged off… so the planet cools somewhat altogether… could this mean that rain/snow falls all the time while this is happening?…
…but hey, surely someone else has thought of all this?? I haven’t read Velikowsky and I don’t know what he said about the Younger Dryas though I get the impression that scientists rather ganged up on him for daring to think afresh. I’m just exercising my own freedom of thought.
Just starting from the assumption they have made that the fresh water somehow will cause enough turbulence to thoroughly mix with the colder denser salt water, I have basic problems with the entire post. Having watched the results of simulations of cold/hot fluid mixing from supercomputer modeling that were verified by physical experiments, it doesn’t happen smoothly, homogeneously, nor quickly. The real physical boundary layer can prevent, under some circumstances, any mixing at all. Sometimes the boundary oscillates for a long time. They have to have assumed that neither happened, because there is no discussion of the possibility.
NFS funding does require that you toe the line, don’t you know…
Arctic Basin salinity is a key variable.
Everything that I have read shows that Lake Agassiz either drained into Hudson Bay or south into the Mississipi River system. I dispute this finding
First of all some supportive statements for the article:
There is geological evidence that glacial lake outbursts did occur from Lake Agassiz into the Arctic Ocean via the McKenzie River at the times specified (I’m not going to supply the references because they are available to anyone willing to read Wikipedia).
The computer model they used shows that the likelihood of a glacial lake outburst via the McKenzie causing a thermohaline current disruption is far greater than through the St. Lawrence or the Mississippi.
Now some criticism of the article:
That a thermohaline current disruption caused the Younger Dryas period is an unproven hypothesis, there are several other hypotheses which are also unproven.
A simple glance at a topographical map shows that Lake Agassiz, given its location and depth, would also have been draining into the St Lawrence and Mississippi watersheds, both of which supply ample geological evidence of this happening. It couldn’t drain into Hudson’s Bay because the ice sheet was still covering that – of which there is also ample geological evidence. I think it’s also reasonable to assume that glacial lake outbursts could have occurred down those routes as well, since ice dams occur on a regular basis in rivers which form ice in the winter.
A computer model does not supply evidence, it supports a hypothesis based on the data supplied and the computations undertaken. Use of a supercomputer does not improve the resolution, the amount of data supplied improves resolution. A supercomputer only speeds up the processing of the data and the same can be done using desktop computers linked in a network and the reference of using it is only a canard to help lend legitimacy to their conclusion.
I realize that this is only an article about the research undertaken, so it would be interesting to actually read their findings rather than read quotes which have been taken and are possibly out of context. It would also be interesting to read about how their computer model was constructed so that its accuracy can be assessed and critiqued properly.
John Marshall says:
Science is a practical subject and needs hands on experiment to learn not a computer.
I’m beginning to think Science is dead. Or at least on its death bed.
I always hate these news blurbs written by people who don’t understand science.
The abstract is available at: http://www.pnas.org/content/early/2012/10/31/1207381109.abstract?sid=b776f87a-3326-4014-ad48-dc853b8dcd82
The article is paywalled.
hm – didn’t get the follow confirmation. Trying again
[Reply: That is because the comment “ignore – following comments” automatically goes into the Trash folder. Unless you can provide a good reason to post such a cryptic comment. — mod.]