From the University of California at Santa Barbara -By Julie Cohen |
Most of North America’s megafauna — mastodons, short-faced bears, giant ground sloths, saber-toothed cats and American camels and horses — disappeared close to 13,000 years ago at the end of the Pleistocene period. The cause of this massive extinction has long been debated by scientists who, until recently, could only speculate as to why.
A group of scientists, including UC Santa Barbara’s James Kennett, professor emeritus in the Department of Earth Science, posited that a comet collision with Earth played a major role in the extinction. Their hypothesis suggests that a cosmic-impact event precipitated the Younger Dryas period of global cooling close to 12,800 years ago. This cosmic impact caused abrupt environmental stress and degradation that contributed to the extinction of most large animal species then inhabiting the Americas. According to Kennett, the catastrophic impact and the subsequent climate change also led to the disappearance of the prehistoric Clovis culture, known for its big game hunting, and to human population decline.
In a new study published this week in the Journal of Geology, Kennett and an international group of scientists have focused on the character and distribution of nanodiamonds, one type of material produced during such an extraterrestrial collision. The researchers found an abundance of these tiny diamonds distributed over 50 million square kilometers across the Northern Hemisphere at the Younger Dryas boundary (YDB). This thin, carbon-rich layer is often visible as a thin black line a few meters below the surface.
Kennett and investigators from 21 universities in six countries investigated nanodiamonds at 32 sites in 11 countries across North America, Europe and the Middle East. Two of the sites are just across the Santa Barbara Channel from UCSB: one at Arlington Canyon on Santa Rosa Island, the other at Daisy Cave on San Miguel Island.
“We conclusively have identified a thin layer over three continents, particularly in North America and Western Europe, that contain a rich assemblage of nanodiamonds, the production of which can be explained only by cosmic impact,” Kennett said. “We have also found YDB glassy and metallic materials formed at temperatures in excess of 2200 degrees Celsius, which could not have resulted from wildfires, volcanism or meteoritic flux, but only from cosmic impact.”
The team found that the YDB layer also contained larger than normal amounts of cosmic impact spherules, high-temperature melt-glass, grapelike soot clusters, charcoal, carbon spherules, osmium, platinum and other materials. But in this paper the researchers focused their multi-analytical approach exclusively on nanodiamonds, which were found in several forms, including cubic (the form of diamonds used in jewelry) and hexagonal crystals.
“Different types of diamonds are found in the YDB assemblages because they are produced as a result of large variations in temperature, pressure and oxygen levels associated with the chaos of an impact,” Kennett explained. “These are exotic conditions that came together to produce the diamonds from terrestrial carbon; the diamonds did not arrive with the incoming meteorite or comet.”
Based on multiple analytical procedures, the researchers determined that the majority of the materials in the YDB samples are nanodiamonds and not some other kinds of minerals. The analysis showed that the nanodiamonds consistently occur in the YDB layer over broad areas.
“There is no known limit to the YDB strewnfield which currently covers more than 10 percent of the planet, indicating that the YDB event was a major cosmic impact,” Kennett said. “The nanodiamond datum recognized in this study gives scientists a snapshot of a moment in time called an isochron.”
To date, scientists know of only two layers in which more than one identification of nanodiamonds has been found: the YDB 12,800 years ago and the well-known Cretaceous-Tertiary boundary 65 million years ago, which is marked by the mass extinction of the dinosaurs, ammonites and many other groups.
“The evidence we present settles the debate about the existence of abundant YDB nanodiamonds,” Kennett said. “Our hypothesis challenges some existing paradigms within several disciplines, including impact dynamics, archaeology, paleontology and paleoceanography/paleoclimatology, all affected by this relatively recent cosmic impact.”
– See more at: http://www.news.ucsb.edu/2014/014368/nanodiamonds-are-forever#sthash.Jz8DHJU3.dpuf
h/t to David Hagen.
Interesting science. Love the new presentation of WUWT!
There’s always going to be arguments about. Hopefully research & time will provide a reasonably solid answer.
The prospect of a devastating hemispheric blast so recent is a bit chilling.
beng –
You haven’t heard it all yet. Google “8.2 kya event”. That is 4,600 years even MORE recent. And then if you dare, start googling different ancient people’s accounts of serious stuff going on in the sky and raining down stuff – not only in the time of man, but also in the time when the accounts are still around. Those accounts aren’t useful battling against entrenched scientific thinking, but they all seem to say that their people saw something happen.
Recently.
So you’ve got reason to be chilled by the idea. That’s why some people are working hard to get NASA to do some space defending – at least begin to prepare.
“You haven’t heard it all yet. Google “8.2 kya event””
That’s BTW exactly the time Plato gave for the sinking of Atlantis.
From wikipedia:
“The 8.2 kiloyear cooling event may have been caused by a large meltwater pulse from the final collapse of the Laurentide ice sheet of northeastern North America—most likely when the glacial lakes Ojibway and Agassiz suddenly drained into the North Atlantic Ocean.[10][11][12] The same type of action produced the Missoula floods that created the Channeled scablands of the Columbia River basin. The meltwater pulse may have affected the North Atlantic thermohaline circulation, reducing northward heat transport in the Atlantic and causing significant circum-North Atlantic cooling.”
YD was caused by a large comet impact. Please see
http://faculty.nps.edu/mjjaye/docs/Esri%20Jaye%20Presentation%2015July2014%20Submerged%20Canyon%20Formation%20A%20Novel%20Explanation.pdf
Nearly 200 years ago, geologists at The Royal Society ‘proved’ that the lands presently occupied were not inundated by a global flood. True. But that conclusion assumed that the Earth has has its present amount of water since its beginning. That is demonstrably false; presently occupied landscapes were not flooded in this event.
I will present material similar to that found at the link, above, at the upcoming Geological Society of America conference in Vancouver. (The link is to slides from a recent Esri user conference.)
In the words of Plato, this massive comet caused an “extraordinary inundation” – a nearly incomprehensible amount of water….
Interesting read from that link Michael Jaye.
From what I saw in a documentary about the YD extinctions, they believe it was a comet air burst, thus no crater, sort of a mega-Tunguska Event.
Thanks for the interesting link
Submerged canyons on the continental shelf were carved by now submerged rivers flowing on land when sea level was 400 feet lower during glaciations. Those deeper than that are caused by outwash floods, plus submarine earthquakes. among other terrestrial sources. No need to posit a giant comet impact.
While I was skeptical of a 2500 km comet containing 25% ice impacting in such a recent geological period, I found the underwater geological formations interesting. I was aware of the features down to 400 ft. depth from the last glacial sea level, but not the features below that.
I find it interesting that they all seem to terminate near the same depth below sea level. We really don’t know anywhere near as much below the ocean surface as we do for what’s above it. I find it hard to understand how flood outflows could affect the topography to such a depth and then suddenly terminate sharply near the same depth throughout the globe.
Is it because we don’t have detailed imagery below that depth, so we don’t see the details further down?Could it be that sea levels were once at that level? You would think that flood outflows throughout the earth wouldn’t so uniform in volume to terminate at uniform depths.
While I haven’t read much of the literature on this, I’m aware of plate tectonics, undersea currents, flood outflows and landslides being proposed as having shaped the landscape of the seafloor. I’m sure someone well read in undersea geology could provide some knowledge or data.
These are interesting new ideas. BUT: Whereto has all the water gone which must have been on earth during e.g. the jurassic era when great areas of the continents were submerged under sea water???
If I am correct, the deepest canyon from a river draining into the ocean is the Congo. You can clearly see its canyon on Google Earth. You might add it to your list. While your thesis is interesting, it seems like a giant comet producing the volume of water you claim, would create such a huge difference in our understanding of the planet, that someone would have come up with the idea a long time ago. And I think that would have been an extinction event of nearly everything on the planet, far greater than any of the other impact extinction events.
I could see a small comet adding to the present volume of water and a combination of ice melt and comet water raising sea levels a few hundred feet, but to have the earth as dry as you indicate in one of your pictures seems very extreme. Especially since you think it was that dry a mere 6kya.
Judging by the map, somewhere in or around NA there should be an impact site. I does fit nicely with the findings on the East Coast of a sterile sand layer from around that time period indicating a disaster that forced the Clovis survivors westward. There is an impact crater in the Hampton Roads/Norfolk area of VA, but it’s not a candidate, missing by some 35 million years.
This has appealed to me for years.
But I know it has been controversial for years too.
In The Younger Dryas impact hypothesis: A requiem previous such hypotheses were found wanting.
I quote,
Maybe this time it’s different.
The research publication goes to great lengths addressing this and other criticisms. James Kennett is an accomplished, careful, and thorough research scientist.
I agree. If you read all of the YD impact team’s papers, the “forensics” of it all will overwhelm you. He does his homework, and so do the others.
On the other hand, the field work is either sloppy in taking samples from the correct layer, or they take too wide of a sample, which waters down the sample in the lab – which then flattens out the spikes in the data. For several of their papers, the skeptics actually didn’t even DO any field work of their own – making those papers little more than opinion pieces. (I am not making this up.)
It always was different. There was a (2012??) reanalysis of the work which found that the investigators with the negative findings had apparently not found what they did not want to find – confirmation bias. Reanalysis showed the very samples that were found negative for impact markers were loaded with them. The reanalysis work had a very critical discussion of the methods employed.
Confirmation bias is exactly what it seems to me, too.
James Wittke was the one with the rebuttal paper, and it basically shredded all the supposed falsifying evidence. But the skeptics were too dense to recognize that they had been body slammed.
The thing is now even some people that thought this was a possible real thing now think that the skeptics have been successful in tearing the idea down. But basically all the YD team can do is keep testing other evidence. The world seems to simply not get it.
They have probably more evidence for this YD event than Luis Alvarez and his supporters had for the dinosaur killer of 65 million years ago. Sites on 4 continents, more than half dozen materials normally associated with impacts (but, oh no, not in this case…). All that is needed is a crater.
But Peter Schultz working at NASA Ames convincingly showed that a hyper velocity impact onto an ice sheet will likely NOT leave a crater underneath. The crater WAS in the ice itself – which got shattered, melted, vaporized, and blown away. And with it went the crater.
Be aware that the ice sheet was deeper than Barringer Crater. In fact, it was about as deep as Barringer Crater is in diameter. With the ice attenuating the impact, any crater under that spot will likely be FAR differenrt from what is currently allowed as “good craters”.
Wouldn’t that make it “infirmation bias” instead ? 😉
Actually, one of Kennett’s cohorts rebutted that supposed requiem quite thoroughly. I was just re-reading some of that this week. The samples taken were done as if by amateurs – because they sampled the wrong layers. They also did not have an impact specialist on their skeptical team, though they did have a good nanodiamond guy (Tyrne Daulton – who may be heard from again in the near future.
But as Ted Bunch communicated to a friend,
That was back in 2010, about the “Requiem” paper.
You also have to understand that Andrew Scott is a forest fire guy. That is what he studies. But IMHO he also wants forest fires to be important – in much the same way, that Michael Mann and Phil Jones want climatology to be important. If someone comes up with a scenario that aces forest fires, especially if it is a catastrophic hypothesis, that would mean he has to fit his forest fires in as second fiddle.
I just looked them up the other day, and none of their “requiem” team was an archaeologist, with experience taking careful samples from the side of a pit.
In addition, that black layer with the nanodiamonds – spread over 50 million square kms makes it kind of more than just your evreyday, garden variety brush fire.
Well, I’m happy to read it was not CO2!
Andres .. Please give the spin doctors a little more time ;^D
A dry ice comet?
Oh, that could be sublime!
“Well, I’m happy to read it was not CO2!”
Of course not… it’s CO2 that was responsible for the near-vertical temperature readjustment (7) though, as well as (1)… what else could explain it?
or… the proxies of 1/2, 5/6/7 are messed up for some reason. Without those anomalies it looks like a relatively smooth rise.
One of the past theories was that the impact was from a radioactive comet.
This led to the disproportionate killing off of large animals (radioactivity built up in the fat cells).
Also, it was hypothesised that it led to the Carbon dating being messed up causing the recovery to appear like it happened overnight.
I can’t find the paper… I think it was by Firestone.
I remain sceptical but I do like the way “it is consistent” with the evidence
It may have been this that I just found linked on Wikipedia.
Firestone is the originator of the YD impact hypothesis. I heard him give the original presentation at the Clovis in the Southeast conference in 2005. The conference was hosted by an archaeologist, Al Goodyear – which made for some tiresome confusion ;-). The YD marked by an apparent radio-carbon anomaly that correlates with other environmental signatures that mark the YD. However, even if the anomaly is real, it doesn’t seriously change just how abrupt the onset and progression of the YD was.
The radioactive comet idea really is humbug though. Radiocarbon is caused by cosmic rays and not even a comet that glowed in the dark would be that radioactive to begin with. It could not under any circumstances be radioactive enough to generate a global anomaly. Besides, objects coming in from the Oort Cloud or the Kuiper Belt have been in deep space for very long periods, possibly since before the solar system formed. That means that only very long-lived radioisotopes would have survived, and the longer-lived the isotope, the less radioactive it is. No amount of biological amplification is likely to significantly increase the radiation hazard from such isotopes to the point that large mammals would be seriously affected.
Even if the comet was pure plutonium, after impact the remains would be scattered over half of the globe. The total radiation at any location would be too low to kill anything.
Regardless, as the KT impact showed, these things are most stressful on the largest animals anyway, even without postulating a radiation affect.
Firestone and Goodyear? Really? ROTFL.
Or, could it be related to the thunderbolts project?
Very interesting. Didn’t Velocovsky covern an ancient SW American Indian myth of something in the sky to the northeast prior to devastation?
Thanks for that. I will have to try to see about that. I read it like 40 years ago…
Where was the impact? Shouldn’t that crater be evident?
Thought to be over the N American Ice sheet.
It melted.
Convenient.
If it was a stony comet, we might be able to find a widely distributed debris field that points back to the impact point.
That makes the stratigraphic reconstructions really difficult. That’s probably why they’re having such a hard time tying all the evidence together for the event, much less the location. Identifying the plume would be difficult as advancing/receding ices containing ejecta move around and then deposit after melt and runoff. I don’t envy them that task.
tteclod –
No, it is not “convenient.” With expanded glaciers covering down to 40° latitude it is ENTIRELY likely that it hit on the kilometer thick ice sheet. Just as it is likely (more so) for an object to impact the ocean instead of the land. And yet, Tunguska and Chelyabinsk air burst over LAND, which is only 29% of the Earth. Amazing, isn’t it?
Anthony –
I’ve got some interesting stuff on thadebris fieldt. At least A debris field. Not good enough to do anything with yet, though. But amazing and tantalyzing.
NielsZoo –
There are at least three lines of evidence that point to the Great Lakes – but dating on one of them is haywire, so it isn’t quite possible to tie it to the time of the YD onset.
I wish I was an OSL man right now…
Anthony – please see my comment and link, above. It was an extraordinary event – planet changing. Impact is evident at Google Earth/Maps(satellite view).
the 1908 Siberian Tunguska event completely flattened ~2000km^2. air bursting comet or meteorite less than 200meters in size. the YDB would have been substantially larger but it too could have been an airburst. or most heavier impacts over the ocean.
Even Tunguska has craters. For a global event to produce the proposed evidence, carbon nano diamonds, either the air burst would be the source of the carbon, which requires still more complex explanation of the celestial body with adequate carbon to spark the event, or there is an impact site with abundant carbon. One may reasonably estimate a center of impact, then go hunting for the crater. Even glacial concealment should be easy to consider.
Or a swarm of icy Tunguska-sized objects. All air-blasts w/no craters & little stone or metals. The wide area of charcoal/nano-diamond layer supports that postulate.
How about a very large object that broke up in the atmosphere, impacting at a number of places across the NH?
/Mr Lynn
Carbonaceous chondrite: http://en.wikipedia.org/wiki/Carbonaceous_chondrite
There was a paper out in 2007 which said much as the above and mentions nanodiamonds.
KImbo –
Yeah, that is the paper that started it all.
Tunguska created no craters.
Check again.
Was the temperature graph part of the paper? I didn’t see it in the press release and was unable to view the whole paper.
I’d like to know that too.
No it was not. It appears to be something Anthony had on hand to help show what the Younger Dryas cooling period was.
@Jimmy, yes that is correct, from another article. I was time limited this AM. I’m sorry if that confused anyone, I’ll make a note in the body of the article.
Could you give us the reference of that other paper?
Yes, BTW, I like the new format, it flows better and is easier to read. Good work Anthony!
I like the larger figures, and being able to address someone’s comment directly, instead of posting a reference to it waaaaay at the bottom.
“Situation solved. No need to look here again. We’ve done this, now move on to something else.” It’s a nice theory, has some supporting evidence, but is it “solved?” Nothing that deals with the past through proxies is every solved, but it does present a possibility. When did scientists start saying “we solved this” anyway? I always understood that there was no solutions, just theories and possible explanations. How much better these new scientists are than they were, say 50 years ago, because whenever they take on a situation for study, they always “solve it.”
Tom, this is basically climatology. Expect outrageous and unwarranted claims of certainty.
Tom O –
I laughed at that. A little bit of absolutism going back and forth between their papers. One side names theirs a “Requiem” for the YD impact hypothesis. So Kennett has to come back with an in-your-face, too.
Personally, the amount of “forensics” on this impact are quite strong and unassailable. The skeptics tried – and failed. They can only nibble around at the corners, like wolves trying to work a caribou pup out of the herd. They can’t do a thing to the core of it. Especially as there is a “suite” – several different lines of evidence, all pointing to the same thing – an impact. But if all of you think defending CO2 against warmists is a bear, try selling geloogists and astronomers on catastrophism only 170 years after they thought they’d buried The FLood forever.
I am telling you: They will fight this until they are blue in the face. You’ll have to claw Gradualism out of their cold, dead hands. Because if this is right, then during times of catastrophe Gradualism wasn’t working anymore, and that means they’ve lost control of geological history. Even comet Shoemaker-Levy hitting Jupiter 20 good whacks in 1994 (20 years ago now!) didn’t let some of them let loose of their “comets don’t hit planets in our lifetimes” mantra.
The Catastrophe Barrier will make the Clovis Barrier look like child’s play. ESPECIALLY if the darned thing hit on the ice sheet and there isn’t a pristine Barringer-type crater.
Geologists -I are one – recognize catastrophes as numerically insignificant but representationally dominant in the geologic record. The one in a thousand year flood wipes out all evidence of lesser floods AND creates a changs of such great character that it withstands the modifications of everyday processes.
The principle that has survived the Biblical fight re The Deluge, is that the processes we see today are the processes that existed yesterday. With local necessary modifications, they are universal processes, applicable to the surface of Mars and Titan today as much as the Earth of 350 million years ago. That being said, catastophism must be viewed skeptically. Like CAGW, the idea is that the period of concern is or was “special”; normal patterns or expectations are irrevevant. This is a dangerously simple and useful concept, especially if one has a career to consider (Michael Mann), a legacy to create (b. Obama) or a fortune to create for oneself or others (Al Gore).
Still … Comets …
There was a lot going on 12,900 years ago. It strikes me that while disasters generally results from a connected series of small problems, including an extraterrestrial coup-de-gras is a trifle melodramatic. Ain’t saying it’s untrue, just sayin’ the story is a little CNN to warrant grabbing and running with if you don’t like the taste of crow.
Well said, Doug Proctor, below.
the KT boundary was recently revised to 66.038 ± 0.025/0.049 Mya.
Science 8 February 2013:
Vol. 339 no. 6120 pp. 684-687
DOI: 10.1126/science.1230492
Hahahahaha –
I freaking LOVE how they talk about things millions of years in the past as if they really bloody know it was 65 vs 66 – or 66 vs 67. Yep, the Miocene started at dawn on the 1st of January, 12.7000000000000 mya.
When the new Carbon14 calibration curves (IntCal13) came out the YDIH was no longer at 12.9kya; it was at 12.8kya. Literally, there was Analiese van Hoesel bitching and moaning a few weeks later that the whole YDIH is full of crap because some of the layers didn’t match up with the new 12.8kya date. She said they were off by 100 years. Which James Wittke took her to task about.
AS IF! As if they really, REALLY know it is 12.8kya now.
But they will run around the very next day after one of these shifts like the Out-Of-Town Experts that they all claim to be, spouting exact, ROCK SOLID dates – dates that are almost as certain to change in the next 25 years as I am to take another breath in 3, 2, 1.. . . YEP, still here, folks!
(And the FUNNIEST thing is that they pronounce REALLY tight C14 uncertainty ranges – like +/- 35 years at 13,000 years ago. I TOTALLY respect the guys doing it, but the uncertainty bars are just too tight – IMHO. I mean, they just adjusted the calibration curve by THEE TIMES THAT.)
But then people like van Hoesel take the damned things literally. If you are off 40 years, well, to her that is not a match. (Forehead slap time…)
And then there are the dates on the climate reconstructions. They all have error bars for the AMPLITUDE, but they never show error bars for the time element. And that DOE make a difference – especially when homogenizing multiple proxies and many different data sets – all of which DO have error bars on the ages of the samples. It shows up on every C14 test and is there for ice cores, too. But every age of every sample, every tree, is treated as if it, too, is accurate to 7 zeros.
What it does in homogenization of data is that if several close dates have their peaks or valleys shifted in time, that tends to flatten out the rolling averages even MORE. I’ve said before that that is ONE of the reasons Mann’s Hockey Stick has a straight shaft.
End of rant.
What’s the source of the Greenland temp graph in this article?
Showing current temperatures almost as low as LIA 😕
The Data looks like it came from a 1997 paper by Cuffey and Clow reported in the J. of Geophysical Research. The right side of the graph is incorrectly labeled. What is labeled as the MWP is actually the Roman warm period 2,000 YBP with a sharp Dark Ages cooling followed by the MWP 1,000 YBP. The arrow for the present global warming shows the LIA with the tiny blip at 0 BP. The scale of the graph makes the modern warming hard to discern.
It’s not the Roman Warm Period. It’s the Sui-Tang WP, which occurred during the Dark Ages Cool Period. The Roman is to the left.
It’s the GISP2 ice core data from Greenland, Alley et al. (2004): ftp://ftp.ncdc.noaa.gov/pub/data/paleo/icecore/greenland/summit/gisp2/isotopes/gisp2_temp_accum_alley2000.txt
The data start at 0.0951409, which is 95 years “before present”, where “present” is, by convention, 1950. So the point at which the data end, inexplicably marked “Present global warming”, is actually 1854.
DavidR
The graph is somewhat misleading without it being clearly pointed out that ‘present global warming’ actually means 1854. To give proper context it needs to be brought up to date. The modern warming should be at least within touching distance of the MWP no matter what the scale of the graph
tonyb
tonyb
See post below for link to Kobashi et al. (2011). The measured average temperature at the GISP2 site for the decade 2001-2010 was -29.9C, which is almost exactly the maximum on the vertical scale on the above chart. However, note also that Kobashi et al. found higher temperatures in the MWP than Alley et al. using a different method. See figure 1 in the paper (it’s Open Access).
BTW, for those who don’t know, with a resolution of greater than 200 years, ice cores cannot be used for high-res dating. The reason for this poor resolution is that the gases migrate up and down within the ice – giving a kind of a fuzzy view of what the gasses could possibly tell us.
tonyb
It was just a picture of the paper’s figure 1, which you can access from the first link. For some reason the system here didn’t like the format.
This 2011 Open Access GRL paper by Kobashi et al. updates temperatures from the GISP2 site to 2010: http://onlinelibrary.wiley.com/doi/10.1029/2011GL049444/full
See especially Figure 1: http://onlinelibrary.wiley.com/store/10.1029/2011GL049444/asset/image_n/grl28620-fig-0001.png?v=1&t=hzgn1f5y&s=803e3718cd9b6ebf6581aecb5673a4093d019987
DavidR
The second link says ‘Forbidden’ so I cant see Figure 1
tonyb
I think the missing salient point here is how did CO2 cause the Younger Dryas and the subsequent rebound? And maybe more importantly how did CO2 maintain the subsequent stable temperatures?
Could it be that maybe, just maybe CO2 is an inconsequential trace gas?
So if it hadn’t have been for the impact event the warming period would have been another ~4,000 years, pushing the interglacial out to over 14,000 years. Great to know that with this info we really could be on the cusp of a new ice age.
BFL –
The dates are 18,000ya, 12,800ya, and 11,500ya, for the end of the Last Glacial Maximum, the Younger Dryas onset, and the Younger Dryas termination. The YD only lasted 1300 years. (Some say 1,000.)
Seeing as the vast majority of the Pleistocene – which we are still in – was ice ages, these last 11,500 years are distinctly an anomaly. If we head back into one there is SOME chance that it could “take” and we could be SOL.
The pattern of the past interglacial-glacial cycles is that the descent into a colder climate from the previous interglacial is, overall, a relatively gradual process, with the coldest temperatures occurring just before the next interglacial starts with a bang (that is, a rapid climb into a warmer climate). That is one of the reasons why the abrupt cooling back into icy conditions that occurred during the Younger Dryas stands out as something worth investigating. Another reason is that some specialists in human prehistory say that the rapidly deteriorating climate in areas which had enjoyed substantial population growth during the immediately preceding warm period may have led to the invention of agriculture to create a more reliable source of food.
There could have been an impact at the older YDB but we don’t need it to cause whatever the Younger Dryas was. The only proxy that cleary shows large deviations is water/ice isotopes, d18O, d2H and deuterium excess in the ice cores and speleothems of the northern hemisphere. There is not any other record or proxy that supports the conclusions we have drawn from that, on the contrary, nothing fits, for instance this one: http://www.geol.lu.se/personal/seb/Geology.pdf.pdf
But it’s essentail to note that these three isotope excursions are exactly the same during the Dansgaard Oeschger events. Consequently, if you need an extraterrestrial event to explain the Younger Dryas, you’d need to find some 25 more extraterrestrial events during the late Pleistocene to explain the other Dansgaard Oeschger events as well.
More over many of the megafauna did not go extinct at the Younger Dryas boundary. Most species perished much earier world wide, but the iconical Woolly Mammoth thrived during the Yonger Dryas in Siberia and disappeared only well after the start of the Preboreal/Holocene. Moreover we keep witnessing the dismissal of young Mastodon carbon dates in America (and only mastodons), because that’s obviously impossible because the Mastodon died out at the Younger Dryas boundary, so that evidence must be false (what fallacy is that?)
But also youngest date of the extinct giant deer/ Irish Elk from Siberia is 7700 radio carbon years. So why do we think that the megafauna extinction is limited to the Younger Dryas boundary?
Comic impact, sure, why not, but you can’t blame it for all the things we see changing at the end of the Pleistocene.
exactly where are the 25 other events
Yes, people often point out that the Younger Dryas isn’t unique. (But don’t tell the biologists that! – THEY are the ones who made a big deal out of it, LONG before Richard Firestone et al came along with the YDIH.
And that is supposed to shut up YD impact people. None of the others actually says squat about the Dansgaard-Oeschger events. (BTW, don’t forget the Bond events – also at 1470-1500 year intervals, for what it is worth). But I’ve tentatively suspected that the D-O events and the YD impact ARE connected. How so? Well there is something called the “8.2 kya event” (google it), and THAT is one of the Bond events. And THAT one is also suspected of being an impact – by people FAR removed from Firestone and Kennett.
My thinking is very rudimentary, but basically it is to consider that all of the D-O events may possibly be impacts.
As you can tell from the GISP2 graph, those are SERIOUS temperature excursions – 10 or 20 or 30 times as big as what warmists are worried about. And they all come on so damned quickly. That is not Gradualism doing that. Internal system forcings I just don’t think can do that.
Crazy idea? Yeah, that is what everybody tells me. But ten years ago asserting ANY impacts connected with ONE D-O warming would have gotten one an invite to the straight jacket store… We now have TWO. As we here all know, correlation is not necessarily causation. But with two of them matching to Bond events and at least on of the two matching with a D-O event, it seems possible, if not probable.
“But it’s essentail to note that these three isotope excursions are exactly the same during the Dansgaard Oeschger events. Consequently, if you need an extraterrestrial event to explain the Younger Dryas, you’d need to find some 25 more extraterrestrial events during the late Pleistocene to explain the other Dansgaard Oeschger events as well.”
Multiple fragments of the same object. IMO this repeated isotope deviation is evidence for impact, not against.
There is much evidence that the Younger Dryas resulted from ‘sudden’ diversion of Lake Agassiz drainage (meltwater as the southern terminus of the Lauentide ice sheet) from the Mississippi valley hence the Gulf to the St Laurence hence the North Atlantic. This disrupted the thermohaline circulation until the fresh water pulse dissipated.
It is of course possible that a cosmic impact was responsible for the diversion rather than the theorized melting of ice dams.
It is not possible that the Younger Dryas itself was responsible for the North American megafauna extinction event at around this time. Those fauna were adapted to the ice age that was receding, and a return to those conditions per we would not have mattered. Clovis over hunting has always seemed a bit of a stretch. Too many animals, not enough hunters. This does provide a testible alternative. All the megafauna species would have disappeared from the fossil record at the time of the event. Worth researching whether that is true, for example at the La Brea tar pits or other known megafauna deposits like the recent cave (prior waterhole) discovery in Utah IIRC.
Refreshing to read about real science rather than climate ‘science’.
Those hunters had a nuclear weapon in the form of what would later be called a buffalo jump. Stampeding herd animals in the direction of a cliff could wipe out the whole heard. Thus they ended up killing far more than they had too but it was the easiest way to feed and provide animal skins to a tribe. The excess would, of course, rot.
Buffalo jumps were used by the Indians in historic times. Here’s a description from the Lewis and Clark expedition. http://lewis-clark.org/content/content-article.asp?ArticleID=441
And more importantly much safer for the hunters
“Buffalo jumps were used by the Indians in historic times.”
And yet they never managed to make species extinct again. Figures…
Oh wait, what if something caused both the extinction AND the human migration ? We already know from both Triassic-Jurassic and Cretaceous-Paleogene extinctions that when something BAD happens, big animals suffer first and foremost while the most adaptable species strive and benefit from the destruction.
Actually, Wallace Broeker – the man responsible for the Lake Agassiz meltwater hypothesis – a couple of years ago admitted that that idea was a no go.
Check out this WUWT post from June 16, 2012:
http://wattsupwiththat.com/2012/06/16/younger-dryas-the-rest-of-the-story/
Some people have been trying to resurrect the idea by invoking a Mackenzie River meltwater pulse instead – but that one comes out about 4,000 km away, on the farthest side of Canada you can go to from the mouth of the St Lawrence.
At Climate Etc, Rud Istvan refers to an opposing review disputing the cosmic impact evidence by Holliday et al., The Younger Dryas impact hypothesis: a cosmic catastrophe from J. Quaternary Sciences 29: 525-530 (2014).
What, no models!
What kind of climate work is this?
Oh Ja, a planetary impact.
Extinctet mastodonts 13.000 years ago:we’ve got nanodiamonds ’50 million
square kilometers across the
Northern Hemisphere’:what so impactet planet earth:a SUV?
Or maybee:13.000 years ago 13.000 SUV’s impactet planet earth to produce some nanodiamonds colleterating mastotonts.
Time sharing with them other yellow pages all over the planet earth.
Astounded. Hans
I guess the theory that the extreme warming by the Bolling Oscillation which melted so much of the continental ice sheets so quickly thus changing the thermohaline circulation causing a re-glaciation, can be put aside into the corner … for now. So much science; so many theories; when will it all become settled?
Jim… Ask al Gore. He knows everything…. ….;^D
Perhaps the comet caused the sudden warming
GOOD POINT, JimS –
It will never be settled sa long as they keep putting patches on to SOMEHOW make the science explain what the previous idea couldn’t. Not without patches upon patches upon patches – ala MicroSoft and Windows. NOT a good model to follow.
I call the patches “crowbars”, because they pull them out ANY time the have a falsification, and they just pull speculations out of their BUTTS and try to force the new thing to make the old idea fit the inconvenient facts. But piling speculations on top of falsified hypotheses is not science. It’s just hip-shooting and hard heads.
The thing is, that they just need to throw OUT the falsified ideas and stop long enough to derive BETTER ideas from the bottom UP. But they identify too much with one idea, and they don’t seem to let it go. So, what e have is several falsified things still in the mix, cluttering up not only the overall, but the brains of those who stubbornly refuse to let it go.
YDB is rapid but not exceptionally so. Other changes around that period were as great in magnitude and not that much slower.
There was already a huge general cooling since the initial false start to the deglaciation.
The end of YD was more remarkable and this time it stuck.
CO2 levels were low enough at the glacial maximum that the increase would have had a GW effect acting as a positive feedback to whatever was driving warming. A positive feedback would also cause snap changes like YDB and YD end, it works both ways. Methane could also be a cause of GW +ve feedback.
That kind of latching behaviour is typical of +ve feedbacks ( which have to be bounded by stronger negative f/b ).
Maybe. Or, it could be the heat was simply hiding in the deep oceans, like it is doing now. Heat is sneaky that way.
The temperature graph is mislabeled & misdrawn. The supposed Medieval Warm Period is actually the Sui-Tang WP, a warm interval during the Dark Ages Cold Period. The following peak is the Medieval & should be at least as high as the S-T but lower than the Roman. The stretch labeled “Little Ice Age” is the latter DACP. The real LIA comes after the Medieval Warm Period.
http://read-think-b4-u-write.blogspot.com/2011/07/envisioning-information.html
Greenland and Antarctica temperatures over the last ice age for reference. How many Younger-Dryas-type cooling events can you count here.
http://s18.postimg.org/4awjdwew9/New_Neem_Temps_vs_NGRIP_Antarctica.png
Interesting graph, Bill.
Upto about 40ka BP the large events seems fairly well synchronised. I’d guess that phase shift before that are more likely time-scale calibration errors than bipolar disorder, though the main warming leading to deglaciation seems to have started a good 10ka earlier in SH.
As I mentioned earlier those alleged cooling events are the Dansgaard Oeschger events. But what you actually see is the oxygen and hydrogen isotope ratios in the ice cores, which are supposed to be proxies for temperature. However this is a logical fallacy. Affirming the Consequent. If it rains, the streets are wet. The streets are wet, hence it rains. Consequently: when it’s cold the isotopes are low. The isotopes are low, hence it was cold. Not necesarily. How about for instance arid versus moist?
There are plenty of paleontological records that shows that the D-O events really were temperature shifts. Or at least that animals and plants (including humans) reacted as if they were climate shifts.
One thing that we need to be aware of with the Greenland and Antarctic ice cores is that, being high latitude locations the cores may OR may not represent the rest of the world.
Especially if the YD impact idea is true, then Greenland was directly downwind of the event near the Great Lakes (as I see it, anyway). And if the burning in N America was from Alberta to the Carolinas, then that was a broad front of smoke headed toward Greenland, one that could hardly miss the place.
THAT could have had a very quick and very heavy effect on the ice in central Greenland. It would likely have been the most seriously affected place outside mainland N America.
Abstract
“A new stomatal proxy-based record of CO2 concentrations ([CO2]), based on Betula nana (dwarf birch) leaves from the Hässeldala Port sedimentary sequence in south-eastern Sweden, is presented. The record is of high chronological resolution and spans most of Greenland Interstadial 1 (GI-1a to 1c, Allerød pollen zone), Greenland Stadial 1 (GS-1, Younger Dryas pollen zone) and the very beginning of the Holocene (Preboreal pollen zone). The record clearly demonstrates that i) [CO2] were significantly higher than usually reported for the Last Termination and ii) the overall pattern of CO2 evolution through the studied time period is fairly dynamic, with significant abrupt fluctuations in [CO2] when the climate moved from interstadial to stadial state and vice versa. A new loss-on-ignition chemical record (used here as a proxy for temperature) lends independent support to the Hässeldala Port [CO2] record. The large-amplitude fluctuations around the climate change transitions may indicate unstable climates and that “tipping-point” situations were involved in Last Termination climate evolution. The scenario presented here is in contrast to [CO2] records reconstructed from air bubbles trapped in ice, which indicate lower concentrations and a gradual, linear increase of [CO2] through time. The prevalent explanation for the main climate forcer during the Last Termination being ocean circulation patterns needs to re-examined, and a larger role for atmospheric [CO2] considered.”
http://dx.doi.org/10.1016/j.quascirev.2013.02.003
http://ars.els-cdn.com/content/image/1-s2.0-S0277379113000553-gr7.jpg
A drop from >400ppm to 200ppm around YDB for a drop of about 8 degrees C, that’s about 25 ppm/K getting sucked back into sinks on a multi centennial scale. Presumably mainly oceanic absorption.
Considerably larger than figures like 8-10 ppm/K I’ve seen coming from ice cores.
If the calibration is accurate here, it suggests that there is significant physical blurring going in ice samples.
Jimbo and Greg, one need to take the absolute CO2 levels of stomata data with a grain of salt. Stomata data have a much better resolution than ice core data, but they are a proxy for local CO2 levels over land, not background levels as the ice core CO2 data are.
Local CO2 over land in general is higher than background, as a lot of organic debris decays over the year(s). In cases of abrupt climate change like the Younger Dryas was, the amount of debris can change a lot, as plant growth (and this its debris) is a lot less at colder temperatures. With as result a change in local CO2 bias. The main wind direction also can have changed and the plant growth/plant types in the main wind direction…
Anyway, while the ice cores resolution is worse, that doesn’t change the average CO2 level of the ice core over the time of resolution, as there is no measurable diffusion in ice cores. Thus if the average of the stomata data differs from the ice cores over the period of the latter’s resolution, then the stomata average is certainly wrong.
The complete paper is avalable here:
https://www.academia.edu/2949675/Stomatal_proxy_record_of_CO2_concentrations_from_the_last_termination_suggests_an_important_role_for_CO2_at_climate_change_transitions
It contains data from several öther stomatal studies that supports the results. There apparently really were rises and drawdowns of 100 ppm or more in just a century or so.