Wrote the book
Recent Developments in the Analysis of the Black Mat Layer and Cosmic Impact at 12.8 ka
Article first published online: 6 DEC 2013
Geografiska Annaler: Series A, Physical Geography
Recent analyses of sediment samples from “black mat” sites in South America and Europe support previous interpretations of an ET impact event that reversed the Late Glacial demise of LGM ice during the Bølling Allerød warming, resulting in a resurgence of ice termed the Younger Dryas (YD) cooling episode. The breakup or impact of a cosmic vehicle at the YD boundary coincides with the onset of a 1-kyr long interval of glacial resurgence, one of the most studied events of the Late Pleistocene. New analytical databases reveal a corpus of data indicating that the cosmic impact was a real event, most possibly a cosmic airburst from Earth’s encounter with the Taurid Complex comet or unknown asteroid, an event that led to cosmic fragments exploding interhemispherically over widely dispersed areas, including the northern Andes of Venezuela and the Alps on the Italian/French frontier. While the databases in the two areas differ somewhat, the overall interpretation is that microtextural evidence in weathering rinds and in sands of associated paleosols and glaciofluvial deposits carry undeniable attributes of melted glassy carbon and Fe spherules, planar deformation features, shock-melted and contorted quartz, occasional transition and platinum metals, and brecciated and impacted minerals of diverse lithologies. In concert with other black mat localities in the Western USA, the Netherlands, coastal France, Syria, Central Asia, Peru, Argentina and Mexico, it appears that a widespread cosmic impact by an asteroid or comet is responsible for deposition of the black mat at the onset of the YD glacial event. Whether or not the impact caused a 1-kyr interval of glacial climate depends upon whether or not the Earth had multiple centuries-long episodic encounters with the Taurid Complex or asteroid remnants; impact-related changes in microclimates sustained climatic forcing sufficient to maintain positive mass balances in the reformed ice; and/or inertia in the Atlantic thermohaline circulation system persisted for 1 kyr.
The hypothesis that a cosmic impact could have generated the YD reversal is still hotly debated in the literature (Haynes 2008; Pinter and Ishman 2008; Ge et al. 2009; Kenntt et al., 2009). Recent critical reviews of the YD event by Van der Hammen and Van Geel (2008) and Broecker et al. (2010) argue, respectively, that charcoal in paleosols of the Allerød–YD transition were not caused by impact, and that the impact event, by itself, could not have caused a glacial advance lasting 1 kyr. The evidence reported here conclusively contradicts alternative hypotheses for the onset of the YD glacial advance, with the most conclusive evidence coming from aerodynamically modified Fe spherules and microspherules, melted and contorted quartz and other lithologies, and carbon mats welded to various minerals.
Long ago the Tusk noted a fascinating 2010 missive from The Bos concerning the virtue of everyone (else) remaining intellectually flexible. Or, as he put it, having a willingness to “change your mind.” Here is the link and I have copied the text at the bottom.
The Bos’ statement has not aged well. I attended his 2009 AGU Session and I shared his admiration of Wally Broecker’s willingness to change his mind regarding YD initiation via a St. Lawrence floodway. It was kinda of neat to be there in person when a major theory took a turn with the driver at the wheel. In retrospect, though, I doubt The Bos would make his current appeal using Broecker as his example.
Here is The Bos’ concluding remark where he recommends Broecker to the YDB team as an example of a nimble intellect following the data wherever it may lead:
The Younger Dryas impact proponents would do well to follow his example.
When Scientists Actually Change Their Minds, Mark Boslough, Skeptical Inquirer, May / June 2010
And here is Broecker himself this year concerning the Younger Dryas impact in NatGeo:
“Most people were trying to disprove this,” said Wallace Broecker, a geochemist and climate scientist at Columbia University’s Lamont-Doherty Earth Observatory. “Now they’re going to have to realize there’s some truth to it”.
Did a Comet Really Kill the Mammoths 12,900 years Ago?, National Geographic online, September 10, 2013
So, The Bos makes a sanctimonious appeal to actively publishing research scientists to change their minds and drop their theory, using as his exemplar a scientific authority who later re-considers his own previously critical opinion of the same theory — a theory to which The Bos himself remains implacably opposed?! How rich!
Perhaps The Bos should take his own advice in the New Year, personally follow Broecker’s example, and carefully re-consider the YDB impact as a legitimate subject deserving further study.
As a graduate student in 1980, I was interested in impact cratering. I had just finished reading the comet catastrophe novel Lucifer’s Hammer when Luis Alvarez, the famous physicist from Lawrence Berkeley, came to Caltech to present a colloquium on his group’s asteroid hypothesis. It made so much sense. What else but an impact could possibly cause a global climate catastrophe and mass extinction?
Many years later, I read an article that featured Wallace Broecker, the Columbia University scientist with revolutionary ideas about catastrophic climate change caused by abrupt slowdowns in ocean circulation. I was fascinated by his idea that the rapid onset of the Younger Dryas cold spell could have been caused by the collapse of an ice dam and a deluge of freshwater into the North Atlantic that shut off the Gulf Stream, stopping the flow of tropical heat to the northern continents and plunging them into ice-age conditions. He showed that there could be other causes of global catastrophes that don’t involve impacts.
I was delighted when Broecker agreed to give the opening presentation at the American Geophysical Union (AGU) session I helped organize, but I was surprised to learn that he had abandoned his famous hypothesis about the cause of the Younger Dryas. He started his presentation by reminding everyone that he used to argue that it was triggered by the flood from the ice-age Lake Agassiz, but when he flew over the route the floodwaters should have followed, he saw no geomorphic evidence for a flood. He had changed his mind!
His primary objections to the impact hypothesis were the same as his objections to the flood he had previously championed as the explanation: lack of evidence and lack of uniqueness of the Younger Dryas. Abrupt changes in climate, both warming and cooling, have happened many times, and Broecker argues that the climate system is inherently unstable. Why should only one of a long sequence of changes have such an improbable and catastrophic trigger event—whether impact or flood—when the climate system has repeatedly undergone such changes all by itself?
In his 1987 CSICOP address, Carl Sagan said, “In science it often happens that scientists say, ‘You know that’s a really good argument; my position is mistaken,’ and then they actually change their minds and you never hear that old view from them again… . I cannot recall the last time something like that has happened in politics or religion.”
Broecker’s esteem among scientists was not diminished when he changed his mind. The Younger Dryas impact proponents would do well to follow his example.
Mark Boslough was co-organizer of the AGU Younger Dryas session in December. He is a physicist at Sandia National Laboratories and an adjunct professor at the University of New Mexico.
Mark Boslough is a physicist at Sandia National Laboratories and adjunct professor at the University of New Mexico. His work on comet and asteroid impacts has been the subject of many recent TV documentaries and magazine articles. He believes that the impact risk—at its core—is primarily a climate-change risk, and he has turned his attention to climate change as a looming national security threat. The opinions expressed here are his own.
It is safe to say The Bos is becoming obsessed. Someone please count and let me know, but I believe he has four publications this year seeking to undermine the Younger Dryas Boundary Hypothesis. Over time he has published more than a dozen. Today he is back in PNAS — alone — and in the face of Harvard scientists who independently discovered to their surprise an extraordinary spike of Platinum in the Greenland ice core at precisely the point in time predicted by YDB hypothesis.
It is also fair to say The Bos has staked his professional reputation on the non-occurrence of the climate changing Younger Dryas impact. He has never hedged his bet in the least, which is an interesting position considering the nature of the purported event. Either a globe cooling cosmic encounter happened ~12,875 years ago — or it didn’t. It might take a decade or two (dammit) but the reality of the event will be determined one way or another. It has a binary quality.
If Mark Boslough has calculated wrong, he will judged one of the most damaging skeptics in the history of science. He has fought mightily, and I would argue quite spitefully, to bury an idea. Find a single example of him calling for further research into the YDB impact and I will buy you a Coke.
So as proof builds for such an impact one would certainly think he would become anxious and more hesitant. Oh, no. He publishes more! I would not be surprised if The Bos frequents Vegas. He certainly seems to have a taste for the dice.
PNAS-2013-Boslough-E5035 by George Howard
PNAS-2013-Petaev-E5036 by George Howard
Live Science article
Did a 6th Century Comet Bring Global Famine?
Evidence from tree rings and ice cores suggest that parts of Europe, Asia and North America saw protracted cooling in the 530′s, which has been linked to drought and famine. Some scientists hypothesize that Halley’s Comet may have caused this, by leaving a dust trail that the Earth later intercepted during its orbit. Dust in the air could have blocked the sun’s rays. Abbott finds evidence in ice cores drilled from Greenland: as much as 10 times more dust is found in the layer corresponding to 533 A.D. than at other intervals, she says. This dust is rich in markers of extraterrestrial origins such as nickel and iron oxide spherules. She finds that neither volcanism nor solar cycles can fully explain the cooling seen in various records during this decade. Furthermore, spikes of the ice-core dust appear to match the timing of the Eta Aquarid meteor shower, known to be triggered by Halley.
Wednesday, Dec. 11, 8 a.m.-12:20 p.m., Posters A-C Moscone South. PP31B-1869
|CONTROL ID: 1810251
|TITLE: What caused terrestrial dust loading and climate downturns between 533 and 540 A.D.?
|AUTHORS (FIRST NAME, LAST NAME): Dallas H Abbott1, Dee L Breger3, Pierre E Biscaye1, John Arthur Barron4, Robert A Juhl2, Patrick McCafferty5
|INSTITUTIONS (ALL): 1. Lamont-Doherty Earth Obs, Palisades, NY, United States.
2. Independent Researcher, Tokyo, Japan.
3. Micrographic Arts, Saratoga Springs, NY, United States.
4. USGS, Menlo Park, CA, United States.
5. Queens University, Belfast, Ireland.
|ABSTRACT BODY: Sn-rich particles, Ni-rich particles and cosmic spherules are found together at four stratigraphic levels in the GISP2 ice core between 360 and 362 meters depth. Using a previously derived calendar-year time scale, these particles span a time of increased dust loading of the Earth’s atmosphere between 533 and 540 A.D. The Sn enrichments suggest a cometary source for the dust. The late spring timing of extraterrestrial input best matches the Eta Aquarid meteor shower associated with comet 1P/Halley. The increased flux of cometary dust could explain a modest climate downturn in 533 A.D. The profound global dimming during 536 and 537 A.D. cannot be explained merely by a combination of cometary dust and a modest volcanic eruption. We found tropical marine microfossils at the end 535-start 536 A.D. level that we attribute to a low-latitude explosion in the ocean. This additional source of dust is probably needed to explain the solar dimming in 536-537 A.D. In addition, we found high-latitude marine diatoms and silicoflagellates at a second time horizon, circa 538 A.D. Some of the fossils are pre-Pleistocene in age, as old as Eocene. Both of these fossil-bearing stratigraphic levels contain enrichments of nitrate and ammonium in their supernatant water.
|KEYWORDS: 0305 ATMOSPHERIC COMPOSITION AND STRUCTURE Aerosols and particles, 4306 NATURAL HAZARDS Multihazards, 0724 CRYOSPHERE Ice cores, 6015 PLANETARY SCIENCES: COMETS AND SMALL BODIES Dust.
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|Previously Presented Material: 10% previously presented at March 2013 meeting on Volcanism, Impacts and Mass Extinctions-material is submitted to a special GSA volume from that meeting
|CONTACT (NAME ONLY): Dallas Abbott
|CONTACT (E-MAIL ONLY):
Readers will recall the awkwardly titled September post, “NatGeo actually calls Wally Broecker to discuss evidence for cosmic impact at Younger Dryas start.” The Tusk was trying to convey there my astonishment that a thoughtful and thorough article was written on recent advances in the study of the Younger Dryas Boundary. Only later, with very little digging, did I realize this was not simply a case of a reporter stumbling on to illuminating facts — but likely a “tell” of greater significance.
It turns out that eminent ancient climate scientist Broecker and reporter Robert Kunzig are hardly strangers. In fact, they share a deep and productive relationship pre-dating this particular National Geographic article on the Younger Dryas Boundary Hypothesis.
Interesting photo of Robert Kunzig
In 2009 Broecker and Kunzig co-authored a fine book, “Fixing Climate,” which the Tusk just finished reading. Fixing Climate is recommended to anyone who enjoys biography in the service of telling a good scientific tale. Nearly all of the book is the personal story of Wallace Broecker and his discovery and explanation of abrupt changes in climate, in particular our favorite period, the Younger Dryas. Broecker’s story is the story of Younger Dryas science in large measure, and a narrative of his life is a wonderful and exciting way to tell the story of the YD.
Fat Tusk and Wally
Which brings me to what I find most interesting about their relationship in the context of our subject. It seems to me the article from September was no accident. The Tusk is supposing that Wally was tipping his writer buddy off to what he knew was building evidence for something extraordinary — and cosmic — having initiated his signature climate period. (Recall that Paetev et. al., discovered a 1000 fold increase in Platinum at the YDB, gives first credit to Broecker (for obtaining access to the Greenland ice core from what I understand)).
As Wally is clearly coming around to the reality of the YD team’s claim, it seems obvious Kunzig was the recipient of a friendly tip from his pal that something big may be on the horizon.
“Most people were trying to disprove this,” said Wallace Broecker, a geochemist and climate scientist at Columbia University’s Lamont-Doherty Earth Observatory. “Now they’re going to have to realize there’s some truth to it”
Broecker to Kunzig — “Did a Comet Really Kill the Mammoths 12,900 Years Ago?” NatGeo, September 2013
Annelies Van Hoesel (Dr. Van Hoesel yet?) recently published an overview of Younger Dryas Boundary Hypothesis in Quaternary Science Reviews. I hear at least one of the YDB authors found it terribly biased against the impact. But it seems to me that she is implicitly admitting that the many obituaries of the YDB impact have been premature. In this game that counts as a win.
The Younger Dryas impact hypothesis: a critical review by George Howard