The Single Biggest Problem With the Younger Dryas Impact Hypothesis: Uniformitarian Impact Craters, Part Cinq

Guest commentary by David Middleton

  • YDIH = Younger Dryas Impact Hypothesis
  • YDB = Younger Dryas Boundary

Last month I shot a big hole in the latest YDIH paper.  This Science News article shoots another big hole in it.  The irony is that both of these particular holes were preexisting conditions: The contradictory data were either unknown to or ignored by the YDIH proponents.

Why won’t this debate about an ancient cold snap die?

Despite mainstream opposition, a controversial comet impact hypothesis persists

BY CAROLYN GRAMLING 2:00PM, JUNE 26, 2018

[…]

Geologists call this blip of frigid conditions the Younger Dryas, and its cause is a mystery. Most researchers suspect that a large pulse of freshwater from a melting ice sheet and glacial lakes flooded into the ocean, briefly interfering with Earth’s heat-transporting ocean currents. However, geologists have not yet found firm evidence of how and where this happened, such as traces of the path that this ancient flood traveled to reach the sea (SN: 12/29/12, p. 11).

But for more than a decade, one group of researchers has stirred up controversy by suggesting a cosmic cause for the sudden deep freeze. About 12,800 years ago, these researchers say, a comet — or perhaps its remnants — hit or exploded over the Laurentide Ice Sheet that once covered much of North America (SN: 6/2/07, p. 339).

[…]

The latest salvo came in March, when West and more than two dozen researchers published a pair of papers in the Journal of Geology. The papers include data from ice cores as well as sediment cores from land and sea. The cores contain signatures of giant wildfires that support the idea of a widespread burning event about 12,800 years ago, West says.

[…]

The March papers focus mainly on the wildfires, a long-standing aspect of the original hypothesis. Greenland ice cores show peaks in ammonium dating to the onset of the Younger Dryas, which the researchers say, suggests large-scale biomass burning. These data were previously presented in 2010 by astrophysicist Adrian Melott of the University of Kansas in Lawrence and colleagues. They suggested that the ammonium ions in those ice cores could be best explained by an extraterrestrial impact. A similar spike dating to 1908 — the year of the airburst over Siberia — had also been found in those same cores. The papers also describe finding peaks in charcoal that date to the start of the cold snap.

“The big thing here is a careful comparison of [many possible impact markers], normalized to the same dating method,” says Melott, one of the authors on the new impact papers. Those markers, including previously described evidence of microspherules, iridium and platinum dust, are consistent with having been caused by the same event, he says.

However, Jennifer Marlon, a paleoecologist and paleoclimatologist at Yale University and an expert on biomass burning, has taken her own look at sediments in North America dated to between 15,000 and 10,000 years ago. She sees no evidence for continent-wide fires dating specifically to the onset of the Younger Dryas.

“I’ve studied charcoal records for many years now,” Marlon says. In 2009, she and colleagues reported data on charcoal and pollen in lake sediments across North America. Importantly, the sediment records in her study encompassed not only the years of the Younger Dryas cold episode, but also a few thousand years before and after.

Her team found multiple small peaks of wildfires, but none of them were near the beginning of the Younger Dryas. “Forests burn in North America all the time,” she says. “You can’t find a cubic centimeter of sediment in any lake on this continent that doesn’t have charcoal in it.”

070718_cg_dryas_inline_6_graph_730

Missing peak: Charcoal records from 15 lake sediment cores from across North America show how often fires occurred at each site over 5,000 years. The records show no peak in burning about 12,800 years ago, as would be expected if there were continent-scale fires.

Such fires could be triggered by rapid climate change, when ecosystems are quickly reorganizing and more dead fuel might be available. “That can cause major vegetation changes and fires,” Marlon says. “We don’t need to invoke a comet.”

The problem with the data in the recent papers, Marlon says, is that the researchers look only at a narrow time period, making it difficult to evaluate how large or unusual the signals really were. From her data, there appeared to have been more burning toward the end of the Younger Dryas, when the planet began to warm abruptly again.

“That speaks to my fundamental problem with the biomass burning part of the papers,” Marlon says. “I don’t understand why they’re zooming in. It’s what makes me skeptical.”

Holliday echoes that criticism. “Most of the time they sample only around this time interval,” he says. What would be more convincing, he says, are data from cores that span 15,000 to 20,000 years, sampled every five centimeters or so. “If this is a unique event, then we shouldn’t see anything like it in the last 15,000 years.”

West says that other peaks are irrelevant, because the impact hypothesis doesn’t imply that there was only one wildfire, just that one occurred around 12,800 years ago. He adds that the new papers suggest that Marlon and her colleagues didn’t correctly calibrate the radiocarbon dates for their samples. When done correctly, he says, one spike in fires that Marlon estimated at around 13,200 years ago actually occurred several hundred years later — right around 12,800 years ago.

[…]

Science News

Why won’t the YDIH debate die?  Mostly because it’s fun and also because its proponents tunnel-vision on the YDB and ignore any observations that are inconsistent with the YDIH.

While the YDIH has a lot of problems, this is the biggest…

West says that other peaks are irrelevant, because the impact hypothesis doesn’t imply that there was only one wildfire, just that one occurred around 12,800 years ago. He adds that the new papers suggest that Marlon and her colleagues didn’t correctly calibrate the radiocarbon dates for their samples. When done correctly, he says, one spike in fires that Marlon estimated at around 13,200 years ago actually occurred several hundred years later — right around 12,800 years ago.

This is analogous to the biggest problem with AGW: There is no genuine wildfire anomaly to explain.

The Medieval Warm Period, Holocene Climatic Optimum and Eemian are said to be irrelevant because past warming not driven by CO2 has no relevance to recent warming which surely must be driven by CO2.  The fallacy in this line of reasoning is that the recent warming is simply not anomalous.

Temperature reconstruction (Ljungqvist, 2010), northern hemisphere instrumental temperature (HadCRUT4) and Law Dome CO2 (MacFarling Meure et al., 2006). Temperatures are 30-yr averages to reflect changing climatology.  The Good, the Bad and the Null Hypothesis.

Over the past 2,000 years, the average temperature of the Northern Hemisphere has exceeded natural variability (defined as two standard deviations (2σ) from the pre-1865 mean) three times: 1) the peak of the Medieval Warm Period 2) the nadir of the Little Ice Age and 3) since 1998.  Human activities clearly were not the cause of the first two deviations.  70% of the warming since the early 1600’s clearly falls within the range of natural variability.

While it is possible that the current warm period is about 0.2 °C warmer than the peak of the Medieval Warm Period, this could be due to the differing resolutions of the proxy reconstruction and instrumental data.

There is no wildfire anomaly associated with the YDB.  Even if you shift the dates, there’s no anomaly.  Because none of the peaks are anomalous.  An anomaly is a deviation from the norm.  If the norm is a fluctuation between wildfire frequencies of  0.0002 and 0.0003 peaks/site/year, a peak of 0.0003 peaks/site/year is not an anomaly, even if it was exactly at the YDB.  A YDB wildfire anomaly would significantly exceed (>2σ) the normal peak amplitude.

Note: The does not mean that it is incorrect to refer to HadCRUT4, GISTEMP, UAH or RSS as temperature anomalies.  The “norm” in these time series is an average temperature over a reference period.

A lot of the evidence for the YDIH has been very interesting.  Some of it has even been compelling.  However a lot of it has been poorly documented, unrepeatable, found to lack uniqueness and seriously unscientific (Carolina Bays… Argh).

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carol

This post and some of the comments reminds me of CAGW enthusiasts writing book reviews on Amazon without actually reading the book involved. The idea that the Younger Dryas requires an impact crater is a complete red herring. Either David and his soul mate Felix have failed to dig into the subject (is that on purpose) or they are misrepresenting the hypothesis. If you go to http://cosmictusk.com you will find a whole raft of published papers in which it is made clear that no impact crater is required. In addition, the hypothesis can explain not only the Younger Dryas event but the Older and Oldest Dryas events, and more important the big whammy around 40 to 30,000 years ago. This is the time when the mammoth die off was at its worst, when the Neanderthals were wiped out, and when Australian megafauna disappears. Felix clouds the issue with crediting a few thousand Palaeolithic people with wooden spears capable of mass die-offs. That smacks of desperation. Not only that but the hypothesis also continues into the Holocene itself – a recurring cycle of events that can only have a connection with the orbit of not just a comet (but the streams of debris outgassed from said comet/ comets). This includes the 6200BC cooling event and various other tree ring anomalies towards the end of the 5th, 4th and 3rd millenniums. Arch climate sceptic Fred Singer even wrote a book on the subject – 1500 year cycles. This might be an artifact of his computer of course but it may also reflect the orbit or orbits of celestial objects. At this very moment a huge asteroid is sitting out there one hundred million miles from the Earth (visible in a telescope and possibly in binoculars) yet that is in resonant orbit with the rest of the solar system objects and amounts to no threat at all. However, the earth passes through streams of dust and debris every month of the year (hence the shooting stars). These streams are mostly dissipated around space in the inner solar system and are not considered a threat. However, when they formed they would have been very dense streams of material – and if it involved the breakup of comets (or parts of comets) and then some big pieces of rock may have been locked into these streams of material (in what is known as the Taurid complex). The YD theory began as an impact on ice but has since moved on to embrace the idea that what caused the Younger Dryas (and the other events) was the gradual break up of a large comet (or centaur to be more precise). In other words the impact was not an impact but the orbit of the earth moving through a dense stream of material that caused a multiple Tunguska scenario – leaving behind lots of dust locked into the upper atmosphere that had the effect of cooling the planet via an opaque sky. This interestingly is thought to behind the Little Ice Age – not of course anything to do with the comet or centaur above but close approaching comets in the 17th century (as historically recorded) and a more enhanced volcanic scenario (also contributing to the dusty atmosphere). Dust is a feature of the Younger Dryas period – the big problem for the YD people here is that why did it last so long (could an opaque sky last for hundreds of years rather than the normal cooling event as a result of a volcanic explosion). There might be another explanation altogether for the length of the Younger Dryas (and come to that of the Oldest Dryas and the 40 to 30,000 year event). Fred Hoyle suggested the Younger Dryas came to an end because of a space rock landing in the ocean and washing all the dust out of the atmosphere. I’m not saying that is correct, only that greater minds than any of us have seriously considered a comet hypothesis. I could go on but I suggest anyone that wants to find out more goes to Cosmic Tusk and explores some of the published articles in journals. Like sceptic articles on climate you have to seek these out for yourselves. To say there is no comparison with climate science is another red herring. The anti YD event brigade exhibit all the same corralling of the wagons complex as if people are unable to loose their minds from what they were taught in educational establishments. It is a human disability and makes the best of minds somewhat fragile. Surely the whole tone of Watts Up should be scepticism of all consensus science – not just the climate stuff.Why comment on something if you have never adequately exlored it. Most of us can understand climate dissonance because it is obviously hype – but science is 80% theory and no more than 20% fact. The NASA missions to the planets are altering consensus science all the time. Geologists are lucky that nobody very much shines a torch on some of their dubious consensus dogmas.

Felix

Carol,

It appears that on your home planet, the paragraph has not yet been invented.

Nor the scientific method.

Might I suggest that you actually study the topics about which you presume to comment. Mammoths didn’t start dying off until well after 30 to 40 Ka.

The first Australian aborigines weren’t armed just with sticks and stones. They came with fire. And they had a long time in which to wreak their havoc.

Some homework for you (but a sampling):

https://phys.org/news/2017-01-humans-climate-australian-megafauna.html

https://www.uow.edu.au/content/groups/public/@web/@sci/@eesc/documents/doc/uow014698.pdf

http://science.sciencemag.org/content/309/5732/287

https://www.nature.com/articles/nature05471

https://www.nature.com/articles/ncomms10511

https://www.nature.com/articles/454835a

https://web.archive.org/web/20110927111457/http://www.control.com.au/bi2008/299megafauna.pdf

http://science.sciencemag.org/content/335/6075/1483

http://science.sciencemag.org/content/335/6075/1483

Tasmania:

http://www.pnas.org/content/early/2008/08/20/0801360105

https://web.archive.org/web/20110927111457/http://www.control.com.au/bi2008/299megafauna.pdf

carol

Mammoths did suffer a die-off before the end of the Ice Age – and prior to the YD event. This is one of mainstream’s main planks against the YD event. So, the Aborigines were cooking the megafauna, then … but it is also a major argument in the human kill-off debate (as your links show as far as Australia is concerned). Whatever anyone says about humans being responsible for mass die-offs it is a theory – which is the whole point. It is not a fact but you are presenting it as a fact. The YD team also have a theory. It is not a fact. They are presenting ongoing evidence to support their theory – why do you feel a need to criticise it because it doesn’t fit your mainstream ideal. It is going to progress whatever people like you say as that is the nature of the beast. I am neither for it or against it. I just think it is an interesting idea.

Felix

That humans killed megafauna is a fact. Whether they were primarily responsible for their extinction is the best theory explaining observations.

You’re simply wrong about mammoths. They survived on Wrangel Island until about 4000 years ago.

The YDI impact is an hypothesis, not a theory. No valid evidence supports the conjecture.

carol

Picking a straw man again. Mammoths on Wrange island were a dwarf species and nothing like the Ic Age animals as far as size and extent of herds are concerned. The YD boundary effect is a theory – so is your absurd humans were responsible for the mass die-offs (and your failure to link to articles that oppose that view and instead prefer alternative causes such as climate change).

Felix

One of the links I provided to my comment, still under moderation because of so many references, shows that the paleo-Australians ate the eggs of giant flightless birds.

If our relative consumes too many of those, the species would soon be extinct. And why wouldn’t the people do so? Practically free, high quality nutrition.

Similarly, the young and smaller females of big, hard to kill species, would be preferentially preyed upon. Wipe out the females and young, and there goes the largest of megafauna. That’s what the buffalo hunters of the US Great Plains did.

Besides fire, our kinfolk could drive large game off cliffs, into pits or environments where they were trapped. And, of course, there is trapping itself.

The megafauna were naive. Some were slow, especially when cold, like the giant lizards.

It’s easy to see how the first Australians, possibly aided by dogs, readily wiped out the megafauna. Same goes for the Americas and the many oceanic islands, such as Hawaii, New Zealand, Reunion, Madagascar and the Caribbean, on which our species also wreaked havoc.

Felix

Dear Mods,

It has been quite some time since I posted a comment with links to research on extinctions in Oz. I wonder if it’s still under moderation or lost in cyberspace.

Thanks!

Felix

I should have been a bit more patient. Thanks!

carol

I don’t usually make comments on here and over the last 15 years or so have maybe made four or five. I’ve got a couple of book by HH Lamb and I knew straightaway the hockey stick involved botched data. Same goes for this post on the Younger Dryas event. It sticks out a mile that both of you have only a superficial knowledge of the arguments involved. Why would you keep on about a lack of a crater. Why would you take the blog of an amateur such as the crater hunter seriously. He is a guy that in his spare time pores over Google Earth looking for interesting geological oddities. He is not a scientist. He has nothing to do with the YD research (although he may have latched on to the YD event in recent years). It is a straw man argument – just the kind of thing you crtiticise climate scientists for doing. Similarly, Cosmic Tusk was started up by a local to the Carolina Bays and he was interested in the subject long before the YD event became news. He has simply amalgamated the two subjects as of interest on his web site. Nothing mysterious about it at all. Another straw man. I visit Watts Up much more often than I do Cosmic Tusk (by miles) but that is neither here nor there. My point is that you are citing mainstream souces which suit your particular bandwagon – and ignoring those contrary. You are behaving in exactly the same way as the climate science clique. Take a deep breath. Likewise, the black mat has been highlighted long before the YD people decided to us it as evidence. There was a literature on the Usselo horizon, for example, many years prior to the YD theory first being aired. What the theory did do was prompt research into the black mats and they turned up all over North America and in some parts of Europe. There are probably a whole lot more of them if geologists were to actively seek them out. The whole point of my post was not to argue for or against the YD event scenario but to point out that ridiculing it solely because it contradicts what mainstream says is tantamount to hypocrisy on both your parts. As for arguing about the dates of wild fires you really are in it up to your necks as this issue is compromised by the massive C14 plateaus associated with 40 to 30,000 years ago and at the Younger Dryas boundary. If you are going to rely specifically on C14 dates (Bayesian or otherwise) you can virtully say anything you want to contradict anyone you want. This is of course a problem for the YD people as much as anyone else.
PS – the C14 boundry has been pushed back to 46,000 years ago by Bayesian methodology in case any reader does not know so criticising my use of 40,000 years ago as a limit (or the date of an event) is another straw man. Why do you feel a need to pontificate?

carol

The consensus is now that dingos or dogs were introduced fairly recently, long after the Ice Age let alone the Megafauna extinction event. It occurred to me today when I was picking some raspberries and peas at the allotment that you have a finger in the pie and that is why you wish to rubbish the YD boundary event. I have no axe to grind either way when it comes to the YD boundary event. It is a hypothesis that I find interesing and try to read every update when it comes along. It is a fact that both NASA and ESA are investing millions of pounds into satellites and space telescopes, searching out potential threats from Chelyabinsk objects, and yet people still deny that space rocks didn’t pose a threat in the past. In your case it seems possible you are a supporter of the ‘humans were responsible’ for the mass die offs – even if the numbers of hunter gatherers were small in comparison with the herds of mammoth (let alone the whole herds of horse that were buried on the steppe, as well as musk ox and various other critters). There is a large body of literature out there opposed to the humans were responsible clique -and various theories have been provided (but all of them ignore the cosmic connection because that is against the grain). I suspect that because climate change is usually blamed for the extinctions this is why you oppose climate change in the modern era. Are you a real climate sceptic or simply somebody that finds it useful to send in a few barbs as it actually supports your cause and undermines your opponents on the mass die-offs. I could provide as many links as you provided in support of your hypothesis but why bother. Interested parties will sniff them out by themselves. Personally, I think your ‘humans were to blame’ theory is even more whacky than the YD boundary event hypothesis.

Felix

Dingos were probably on New Guinea and Australia by 8000 years ago.

No one knows whether the first humans to arrive in Australia had dogs or not. But even assuming not, then dingoes could have helped continue the extinction of native fauna after 8000 years ago. The thylacine or “Tasmanian Wolf”, a dog-like marsupial carnivore, only died out in the last century.

carol

So what, islanders in western Scotland ate the eggs of gannets but they aren’t extinct. The dog or dingo arrived in Australia fairly late in the day – long after the demise of the megafauna. The Palaeolithic people were not equipped with repeating rifles such as the Winchester. A recent article (available on PhysOrg and Science Daily) claims Palaeolithic people used wooden spears to hunt deer and other prey. North America is not an island – herds can run away and find a safe space. Try and kill off even a small herd of deer, with dogs as help. Some deer will be killed but others will hide up until its safe to emerge again. Deer can run through thorny bushes which inhibit domesticated dogs for example – and they can leap quite high. Mind you, a good lurcher can take down a deer easily – on a one to one basis. The wildlife of islands like Madagascar, Reunion and Hawaii also suffered from ships crews on long voyages in search of some fresh meat. This is not the case in Australia or North America. This argument could go on and on and never get anywhere. You obviously have a finger in the pie somewhere as you are strongly resistant to the idea of a natural disaster of any kind as it will negate some of your nonsense about humans being responsible for mass die-offs. Sticks out a mile really as it is in fact a rival theory that might explain everything you would like to explain in your version of what happened. Your ideas are equally as whacky as the YD boundary event – but wait a minute. NASA and ESA are spending millions on satellites and space telescopes in order to pin down possible threats of rogue asteroids and objects as small as Chelyabinsk meteors. Why would they do that if space rocks were not a threat. If they are a perceioved threat in 2018 the same goes for 13,000 years ago. You may note the Chelyabinsk space rock exploded in the atmosphere – but it had a powerful blast. The Tunguska object on the other hand is thought to have been somewhat bigger as the blast was capable of knocking down a swathe of forest (admittedly Siberian pine trees do not have the sturdy roots of trees growing in lower latitudes but impressive enough). Imagine several tunguska object in close association (one following the other) and you get the kind of idea central to the YD boundary event. In coming into contact with a dense stream of debris from a comet in the process of breaking up all kinds of scenarios are possible – and a large comet would not break up in one pass around the Sun. However, although it seems to me this is an interesting hypothesis there has yet to be published conclusive evidence, and the argument at the moment revolves around what constitutes evidence of a cosmic intrusion (such as nano diamonds etc). I also understand there are further articles in the pipeline.

JimG1

Thanks David, very interesting but the YDIH is much more exciting to think about and that’s probably why it has stayed around, scientific or not.

Eustace Cranch

That’s exactly what I was going to say. Like UFO’s, Bigfoot and Nessie. The appeal is in the entertainment value.

Bill Watson

That is hardly fair. What exactly is the orthodox view that is so compelling, comprehensive and dull?

Felix

That the YD was just another normal swing in a typical glacial termination, caused by a cold, fresh water release into the North Atlantic.

And that the rate of megafaunal extinctions, if it increased at all, was due to humans, not an impact for which there is no valid evidence.

Tom Halla

Yeah. It’s such a neat theory that it should be true./sarc

Southerncross

And the obvious craters found all over the place are no evidence at all ?

Duncan Smith

To be fair, yes it is a fun theory but there is no other overwhelming theory to kill it. To say any theory is final is wrong, there is even discussion of a new theory of gravity to explain away dark matter. Or possibly the answer is right in this post, what explains the slow but steady rise in the North American fires in the below graph, peaking around 13,000 YBP.

comment image

https://phys.org/news/2016-11-theory-gravity-dark.html

Felix

You’re joking, right?

As the ice sheets retreated, more forests grew and grasslands spread, hence more fuel for wildfires.

There is an overwhelming alternative theory to kill the Krazy Komet Konjecture. It’s the Null Hypothesis. The YD needs no special explanation. It’s just another natural fluctuation in a normal glacial termination, just like all the others in its own termination and all those preceding it during the Pleistocene.

They’re akin to Heinrich Events during glacial periods, ie cold, fresh meltwater events, iceberg armadas in the case of HE and outbreaks of proglacial ice dams during the terminations.

Jeff

The earliest securely dated sites showing human presence in the Americas, 16–13 ka for North America and 15–11 ka for South America.
Humans would have used fire extensively.
They also wiped out the mega fauna around these times.
“During the American megafaunal extinction event around 12,700 years ago, 90 genera of mammals weighing over 44 kilograms became extinct.”

bonbon

Humans Present at Brazil’s Santa Elina Rock Shelter 23,120 Years Ago, Confirms National Museum of Natural History in Paris
http://ancientnews.net/2017/09/07/humans-present-at-brazils-santa-elina-rock-shelter-23120-years-ago-confirms-national-museum-of-natural-history-in-paris/

Just saw a report on links to Africa. Thor Heyerdahl was right.
Australia’s Kimberley rock art dated (by a bees nest) to 25,000BP also has great similarity to Lake Chad art. The only way is by boat, willfully navigating open ocean. The foot-dragging Oxbridge narrative is going the way of fake news.

As I posted on WUWT June 12, 2012 and June 2, 2013, the biggest problem with a cosmic impact is that it is a SINGLE EVENT that cannot possibly explain the abrupt warming near the end of the Pleistocene, followed by an equally abrupt cooling back to full glacial conditions that lasted for 1000 years, followed by abrupt warming to full interglacial conditions. A cosmic event can’t last 1000 years!

Southerncross

What about an interruption of the cooling process ? IE an impact interrupted the natural process which was then overcome by the natural cooling process again ?

Humans are used to measuring things in our own lifetimes, Nature moves in multiple multiples of that type of measurement. An impact on an Ice Sheet could cause such an interruption and leave very little physical evidence, disrupt a cycle and then collapse back into the norm of a natural cycle once again.

Stranger things have happened! Trump got elected for one.

Felix

Umm, the YD was a cooling interval during a longer-term warming, ie the termination of the Wisconsin glaciation. It’s no different from the Older Dryas and Middle Dryas and all such cold snaps before it.

Javier

Don, I have told you several times, but you keep not learning it.

“the abrupt warming near the end of the Pleistocene, followed by an equally abrupt cooling back to full glacial conditions that lasted for 1000 years, followed by abrupt warming to full interglacial conditions.”

The Younger Dryas is not a return to full glacial conditions. You have tunnel vision with Greenland ice cores, and particularly GISP2. Antarctic cores do not show much of a YD, despite being locked to Greenland by the polar see-saw. And LR04 benthic stack barely shows a detectable inflection at the time. The event didn’t register in the planet’s oceans.

comment image

The conclusion is clear. The YD was a North Atlantic event. Not a return to full glacial conditions as you keep saying!!!

The Bølling warming was Dansgaard-Oeschger-1 (DO-1) event. The end of the Intra-Allerod Cold Period (IACP) was DO-A event. The end of the YD was DO-0 event. They are all separated by 1500 years.

comment image

What remains to be explained is the cooling at 12,800 BP. It coincides with a low in solar activity from the 2500-year Bray cycle, but that is not enough by itself. It also coincides with a Heinrich event (H0). The coincidence of both ice/oceanic, and solar looks like a good enough explanation to me. Perhaps there is also contribution from the large Melt Water Pulse 1A that took place right before.

comment image
The 2500-year Bray cycle in ¹⁴C record showing the Younger Dryas as B-6 low.

Felix

The YD is no different from all the other similar cold snaps following hot snaps during glacial terminations.

Javier

I disagree. MIS 1 (Holocene) is the only interglacial that in EPICA Dome C shows a cold relapse at a such critical time.

comment image

The Holocene would probably have been warmer if it wasn’t because of the YD. It looks that it sabotaged the deglaciation at a critical time.

To me it was due to an improbable coincidence of known factors at a really sensitive time. No astronomical causes are needed.

Felix

I wish your graph were in color. It appears that the last termination occurred during lower obliquity.

At that point in other terminations, there were still fluctuations, just not as great, both up and down. Besides a possible Milankovitch factor, IMO the most important difference was the existence of the Great Lakes, such as Minong where Superior is now.

Javier

“Antarctica is out of phase with Greenland.”

Yes, the bi-polar see-saw hypothesis, that has quite a lot of evidence.

It is all part of the same phenomenon likely with multiple causes and interconnected between the two poles.

The deglaciation decreases sea-ice levels enough in the Norther Hemisphere to reactivate the Dansgaard-Oeschger cycle, that was suppressed during the glacial maximum. DO1 event releases a massive amount of accumulated stratified subsurface heat in the Nordic Ocean producing the Bølling warming.

AMOC reactivates due to the decreased sea-ice from the Bølling warming and draws more heat from the South Atlantic. This has the effect of cooling Antarctica due to the see-saw mechanism. The Northern hemisphere cools progressively through the Allerod period. Low solar activity, meltwater discharges, and an altered atmospheric pattern bring about the Younger Dryas cooling. The cooling is so important that triggers the last Heinrich event (H0). This has the effect of reducing AMOC and starting a big Antarctic Isotope Maxima (warming) as a consequence.

comment image

Then the next (and last) DO0 event puts an end to the Younger Dryas.

Pedro et al., 2015 analyze the dynamics of the polar see-saw in the context of the 14700-13000 Antarctic cold reversal

https://www.researchgate.net/profile/Brian_Chase/publication/284104371_The_spatial_extent_and_dynamics_of_the_Antarctic_Cold_Reversal/links/56504b9d08aeafc2aab6d7e4.pdf

And Renssen et al., 2015 are succesful at reproducing a multi-factorial Younger Dryas.

https://dial.uclouvain.be/downloader/downloader.php?pid=boreal:168233&datastream=PDF_01

bonbon

Low solar activity meaning, like now or the LIA, few sunspots and enhanced cosmic ray flux? Basically Svensmark’s hypothesis?

Javier

Low solar activity meaning like during the LIA, much lower than now. But not due to cosmic ray effects as Svensmark proposes, but to direct effect of low solar activity on Earth’s climate.

Martin457

Whenever I read anything about this anymore, I automatically cry out “Planet 9” and start laughing.

bonbon

It is extremely interesting how the science advances in detail – this period is for mankind critical. Now I am going to take a BIG risk here. I know this could trigger a WUWT Tunguska.
Ignoring Emanuel Kan’t’s categorical imperative and focus on the Clovis artifacts, from another forbidden walled-off-from-geology faculty. It is hugely controversial that culture arrived from old europe – the Solutrean idea. That would mean ocean crossing or at least ice shelf navigation. In other words mastery of ocean navigation – forbidden by the “walking” narrative, foot-dragging.
There is yet another mighty Kan’t Wall – that between these two sciences and literature.
Now at the risk the Visigoths will burn Rome – have a look at Plato’s Timaeus. There is a written account handed down for 8000 years (I know, yet another forbidden Kan’t moat, barring oral tradition), for what exactly happened in what the geologists call the YD. And climatologists think they got attacked? Just look at the charlatans around the Timaeus!

What enrages the modern Visigoths? Is it that civilization can have deep roots, language critically important, even before known writing? Is it the fact that Schliemann, an engineer, made utter and complete fools of Oxbridge experts, and found Troy? Based on a written account? Homer was never there and wrote the story was handed down through a dark ages of 800 years, orally. Is it breaking Kan’t categorical imperative?

So let the geology continue with this hugely interesting period.

I’ll just mention Plato described apparently volcanic activity, in the ocean. An abrupt upheaval. Whether triggered by a comet or not, some do say volcanic action can also account for the deposits.

Felix

If Plato had a marine volcano in mind, it would have been a distant folk memory of the Minoan era eruption of Santorini (Thera), not a mythical island continent in the mid-central North Atlantic, for which there is zero evidence.

It would take no great seafaring skills to cross the North Atlantic during the LGM, when it froze over in winter. Eskimos made long trips in skin boats along ice edges in modern times. Glacial sea level was of course much lower then, too, exposing land on both sides of the ocean and amid it, at Rockall.

But the first paleoamericans from Siberia needn’t have walked. Indeed, they probably didn’t. Even the “ice-free corridor” between the receding ice sheets would have been inhospitable then. More likely they came along the coast of Alaska and the Pacific NW in order to get south of the Cordilleran Ice Sheet.

bonbon

Plato’s text is very precise, anything else is mere supposition. He wrote his grandfather told the story from an Egyptian who claimed 8000 years of records. So “folk memory ” is it not. He clearly said the Athenians had no memory at all of the epoch, as, like children, had to start anew. They had even completely forgotten the victory over the invaders from the catastrophe. Thera would have been “folksy”, and is quite fashionable – millions have been spent on moving Plato’s story from the great ocean to the local pool.
The 400 ft lower coastline had probably settlements all around the great ocean, rather like the Black Sea before its inundation. Plato recounts that civilization as being rather tyrannical.
The “Mud and Fire” of the destruction of the entire island in 48 hours is a clue. Whether the catastrophy occured because the ocean was rising or before is not known. The entire coastal settlement area was being (slowly?) inundated.

David L. Hagen

There is evidence for outburst Megafloods from glacier dammed lakes causing rapid freshwater pulses that needs to be considered. e.g.,
Megaflood erosion and meltwater plumbing changes during last North American deglaciation recorded in Gulf of Mexico sediments
Paul A. Brown, James P. Kennett
Geology (1998) 26 (7): 599-602.
https://doi.org/10.1130/0091-7613(1998)0262.3.CO;2
https://pubs.geoscienceworld.org/gsa/geology/article-abstract/26/7/599/206921

Barber, D.C., Dyke, A., Hillaire-Marcel, C., Jennings, A.E., Andrews, J.T., Kerwin, M.W., Bilodeau, G., McNeely, R., Southon, J., Morehead, M.D. and Gagnon, J.M., 1999. Forcing of the cold event of 8,200 years ago by catastrophic drainage of Laurentide lakes. Nature, 400(6742), p.344.
(Cited by 1094 articles.)

Felix

Kennett apparently changed his mind. Why would that be, do you suppose?

John F. Hultquist

I hope someone figures this out in the next few years. Say by 2030.
I’m curious, but won’t hang on much longer than that. As the song says,
I may check out sooner.

Thanks David.

https://www.sciencedirect.com/science/article/pii/003358947790031X

The Gothenburg magnetic excursion also was going on during the time of the YD. I think it may have had some contribution.

bonbon

Would the (unstable?) excursion be a result of massive ice melt? Would it be safe to say an excursion is an instability? I am not sure if the dynamo model is “settled”. OTH these must affect incident high energy radiation and aerosols.
This is a lot more complex than the “CO2” pablum.

Joanne P Ballard

I also have charcoal data for thousands of years prior to 12,800 yrs BP. Yes there are charcoal peaks prior to the YDB in the Bolling Allerod. Conifers were the dominant species in Michigan (my study area) at that time. As Marlon says, wildfires happen without a comet. So how can we differentiate a comet- ignited fire from terrestrial burning that is part of the wildfire regime? We should look for other things that are different than at other times. These include the geochemistry of lake sediments (and ice cores). A platinum spike was found in the Greenland ice cores by Petaev et al 2013. Moore et al. have now found a platinum marker in sediments. There is a widespread black mat that is not a regular feature of sediments today. Haynes 2008 summarizes the locations and characteristics of these black mats (charcoal rich, algal mats), and Van Geel 1989 discusses the late glacial age Usselo horizons in The Netherlands. This is a burn layer with fused quartz, melt glass, soot, charcoal, sponge spicules, and algal evidence that I have seen in 3 localities across The Netherlands and 1 site in Belgium. Although Van Geel wrote a paper in 2008 dismissing the need to invoke a comet, wildfires don’t reach temperatures high enough to fuse quartz grains and melt glass. I will present new data on the YDB impact hypothesis at the AMQUA-CANQUA conference in August in Ottawa, Canada. I will be talking about a new proxy for wildfires. The initial study using this new proxy points to widespread wildfires across eastern North America during the late glacial.

Jeff

Yes comet/meteor impact theories are fun, sensational and headline grabbing,
but untrue IMO.
I also don’t believe the dinosaurs were wiped out by an impact.
Evolution did that – just more advanced species out competing many of the more primitive ones.
Evolution doesn’t require an impact or even a dramatic change in the environment.

Felix

Paleontologists debate the extent to which non-avian dinos were on their way out at the end of the Cretaceous. I don’t think they were, but many disagree.

However, the evidence for a huge impact 66 Ma is overwhelming. And its consequences would have been horrific. All the evidence supports the hypothesis that non-avian dinos and a host of other long-lived groups were wiped out or decimated at the K/T boundary by the effects of an impact on the Yucatan.

Others claim that the Deccan Traps flood basalt eruptions also played a role, as India crossed the Reunion hotspot. IMO, that was minor, at best.

Jeff

Of the five major mass extinction events in Earth’s history, none other than the terminal Cretaceous event has ever been even approximately associated with an impact.
Several other large impact craters besides Chicxulub have been well studied by geologists and none is associated with fossil evidence of extinctions.
Some scientists say the Chicxulub impact preceded the mass extinction by 120,000 years and had little consequence for the fossil record of life.

Felix

Not any more they don’t. The dating is a smoking gun.

It’s unclear about some of the other big MEEs, but based upon the best evidence, I agree with you.

JimG1

David,

Great post with great comments. Thanks again.

JimG1

GUILLERMO SUAREZ

Why did Humans not “wipe out ” the large beast which ,before the arrival of the Europeans inhabited Africa ? Were the inhabitants of American before and after the younger dryas in possession of much more efficient Hunting tools ? Were Mastodons and Mammoths relatively docile creatures , in comparison to their African cousins? Wait, I know , I know, the Africans Co evolved with the large beast , so they feared and understood humans , but the hairy North American ones were incapable of figuring out that the little two legged guys with the spears were a threat , and could easily be squished by a stampede ? A protective maneuver, which most likely was commonly practiced by the herd, against Predators ? The North American invaders had a taste for Pachyderm , but not their African cousins ? What caused the extinction of the Siberian Mammoths ? Why have so many Pachyderm corpses been found intact in North America, and Siberia , but not , I believe, Africa and India ? Yes ,the cold, the Permafrost , may in part explain this fact.However, typically ,carcasses are quickly consumed by scavengers , including bones , but a scores of sites , with multiple Mammoths having soft tissue preserved , have been uncovered. Yeah, the humans lit the tundra on fire and ran them off cliffs , like the Buffalo , thus explaining the extinction of both .But wait, I demur, only the latter species survived the YDP , despite being an easier prey for predatory humans , and only within the past 400 years was almost extinguished by modern weapons , .Perhaps there did exist an advanced civilization ? Ever try to kill a mammoth with a spear? No wonder the Clovis perished.

Bill Illis

” … Yeah, the humans lit the tundra on fire and ran them off cliffs , like the Buffalo ,”

I think creative hunting techniques of humans have been under-estimated. People are not going to stand in front of herd of mammoth but there would have been lots of opportunity to use the landscape or river crossing points to take on the megafauna.

But the Buffalo were just so numerous in North America that it wasn’t until the invention of the Sharps Rifle (50 calibre and extremely accurate) in the 1870s that the Buffalo were taken out in North America.

Keep in mind however, that humans hunted the European and African Buffalo and the cattle ancestor, the Auroch, to extinction long before the invention of firearms.

Felix

The horse had a lot to do with it. Plains Indians would have wiped out the buffalo just with the horse, lance and arrows, given enough time, by concentrating on cows. Add even muzzleloading carbines, and the end would have come more rapidly.

But the Sharps did seal their fate. Buffalo hunters racked up big scores because they could make a stand. Firing at long range, rifle-armed hunters could shoot cow after cow without stampeding the herd.

As Bill notes, the older, bigger species of bison were indeed wiped out by paleoamericans.

bonbon

Those hunters thought just like us – see link above on re-loadable spears from 31,000BP Siberia.
Imagine a squad of Picadors with quivers of replaceable Clovis tips.

First let’s get a couple of preliminaries out of the way

1) Please forget “the Carolina Bays”; that’s a red herring, bordering on “Cointel” as the conspiracy theorists would call it.

2) *SOMETHING* happened in North America at the Younger-Dryas. 35 mammals and 19 bird genera, along with the relatively advanced Clovis people went extinct in a very short time throughout North America. Yes the Clovis people were advanced as stone age people go, but causing massive continent-wide extinctions boggles the mind.

An interesting talk given by a real scientist, not a conspiracy nut, is at

https://www.youtube.com/watch?v=kdR-ODgYZH8

You may want to skip the first 6 minutes, as its a preliminary intro using the KT boundary layer to set up things.

At 8 minutes 23 seconds into the video is a a map of multiple sites in the northern hemisphere where a distal ejecta layer has been found, dating to the Younger-Dryas. Like the KT layer it has iridium spike, glass spherules, nano-diamonds, shocked quartz, etc.

At 25m 30s he points to NASA AMES research which indicates that a 1 km wide body coming in at a low angle hitting a 1 km thick ice sheet would leave a massive crater in the ice, *BUT NOT IN THE LAND SURFACE BENEATH IT*.

He goes on to point to 5 sites in eastern Canada that look interesting, and may actually be at the correct date, unlike the Carolina Bays.

bonbon

On Mesolithic hunting efficiency see :
https://news.nationalgeographic.com/news/2004/01/0114_040114_siberianhumans.html
A modular spear, capable at full running speed to be ‘reloaded’ by attaching new heads that had broken off in the animal . The prey had no chance from a group of well-stocked runners – the Spanish Picador is likely a modern day version. Spear shafts found are of rhinoceros horn and mammoth tusk. Heads seem to be Clovis.
This find is in Siberia’s Yana river from 31,000 BP.

bonbon

The most important thing to check is not the extinction but the type of species afterwards. Every “mass-extinction” is followed by a qualitative uplift. Vernadsky notes the jumps. There is always a speed-up , a metabolic jump, as if the previous mainstream were anyway doomed by a lower metabolic rate.
This kind of action strikes when physical economics fails to progress to higher energy densities. The use of fire which defines mankind, shows jumps from wood to coal, oil, nuclear… of course much faster not waiting for “evolution”, rather only willful ideas. At each jump opportunity, failure would mean collapse.
The entire attack on fossil fuels is actually on what makes us human, not animals. This ancient childhood sickness is behind all civilizational collapses. What we can willfully do, the biosphere did over aeons. Should not be a surprise as we are from that very same biosphere.