Here’s something useful that works like radiocarbon dating, but on ice. Since it is cosmic ray based, it makes me wonder if it could be used to reconstruct the cosmic ray record to test Svensmark’s theory of cosmic ray modulation of climate. How it works (graphic from Argonne National Laboratory):
Kr is a cosmogenic isotope produced in the upper atmosphere. Its analysis allows age determination for:
- dating polar ice to study the climate history of the Earth, and
- dating old groundwater to study the source, sink, and flow pattern of aquifers.
The applicable age range of 100 kyr – 1 MyrĀ is beyond the reach of 14C-dating.
From Oregon State UniversityĀ Ā CORVALLIS, Ore. ā A team of scientists has successfully identified the age of 120,000-year-old Antarctic ice using radiometric krypton dating ā a new technique that may allow them to locate and date ice that is more than a million years old.
The ability to discover ancient ice is critical, the researchers say, because it will allow them to reconstruct the climate much farther back into Earth’s history and potentially understand the mechanisms that have triggered the planet to shift into and out of ice ages.
Results of the discovery are being published this week in the Proceedings of the National Academy of Sciences. The work was funded by the National Science Foundation and the U.S. Department of Energy.
“The oldest ice found in drilled cores is around 800,000 years old and with this new technique we think we can look in other regions and successfully date polar ice back as far as 1.5 million years,” said Christo Buizert, a postdoctoral researcher at Oregon State University and lead author on the PNAS article. “That is very exciting because a lot of interesting things happened with the Earth’s climate prior to 800,000 years ago that we currently cannot study in the ice core record.”
Krypton dating is much like the more-heralded carbon-14 dating technique that measures the decay of a radioactive isotope ā which has constant and well-known decay rates ā and compares it to a stable isotope. Unlike carbon-14, however, krypton is a noble gas that does not interact chemically and is much more stable with a half-life of around 230,000 years. Carbon dating doesn’t work well on ice because carbon-14 is produced in the ice itself by cosmic rays and only goes back some 50,000 years.
Krypton is produced by cosmic rays bombarding the Earth and then stored in air bubbles trapped within Antarctic ice. It has a radioactive isotope (krypton-81) that decays very slowly, and a stable isotope (krypton-83) that does not decay. Comparing the proportion of stable-to-radioactive isotopes provides the age of the ice.
Though scientists have been interested in radiokrypton dating for more than four decades, krypton-81 atoms are so limited and difficult to count that it wasn’t until a 2011 breakthrough in detector technology that krypton-81 dating became feasible for this kind of research. The new atom counter, named Atom Trap Trace Analysis, or ATTA, was developed by a team of nuclear physicists led by Zheng-Tian Lu at Argonne National Laboratory near Chicago.
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  IMAGE: This is the ice core driller Tanner Kuhl with the blue ice drill on Taylor Glacier in Antarctica. The field camp is visible in the background.Click here for more information. |
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In their experiment at Taylor Glacier in Antarctica, the researchers put several 300-kilogram (about 660 pounds) chunks of ice into a container and melted it to release the air from the bubbles, which was then stored in flasks. The krypton was isolated from the air at the University of Bern, Switzerland, and sent to Argonne for krypton-81 counting.
“The atom trap is so sensitive that it can capture and count individual atoms,” said Buizert, who is in OSU’s College of Earth, Ocean, and Atmospheric Sciences. “The only problem is that there isn’t a lot of krypton in the air, and thus there isn’t much in the ice, either. That’s why we need such large samples to melt down.”
The group at Argonne is continually improving the ATTA detector, researchers there say, and they aim to perform analysis on an ice sample as small as 20 kilograms in the near future.
The researchers determined from the isotope ratio that the Taylor Glacier samples were 120,000 years old, and validated the estimate by comparing the results to well-dated ice core measurements of atmospheric methane and oxygen from that same period.
Now the challenge is to locate some of the oldest ice in Antarctica, which may not be as easy as it sounds.
“Most people assume that it’s a question of just drilling deeper for ice cores, but it’s not that simple,” said Edward Brook, an Oregon State University geologist and co-author on the study. “Very old ice probably exists in small isolated patches at the base of the ice sheet that have not yet been identified, but in many places it has probably melted and flowed out into the ocean.”
There also are special regions where old ice is exposed at the edges of an ice field, Brook pointed out.
“The international scientific community is really interested in exploring for old ice in both types of places and this new dating will really help,” Brook said. “There are places where meteorites originating from Mars have been pushed out by glaciers and collect at the margins. Some have been on Earth for a million years or more, so the ice in these spots may be that old as well.”
Buizert said reconstructing the Earth’s climate back to 1.5 million years is important because a shift in the frequency of ice ages took place in what is known as the Middle Pleistocene transition. The Earth is thought to have shifted in and out of ice ages every 100,000 years or so during the past 800,000 years, but there is evidence that such a shift took place every 40,000 years prior to that time.
“Why was there a transition from a 40,000-year cycle to a 100,000-year cycle?” Buizert said. “Some people believe a change in the level of atmospheric carbon dioxide may have played a role. That is one reason we are so anxious to find ice that will take us back further in time so we can further extend data on past carbon dioxide levels and test this hypothesis.”
The paper preprint:Ā http://arxiv.org/pdf/1403.6201v1
Radiometric 81Kr dating identifies 120,000 year old ice at Taylor Glacier, Antarctica
We present the first successful 81Kr-Kr radiometric dating of ancient polar ice. Krypton was extracted from the air bubbles in four ~350 kg polar ice samples from Taylor Glacier in the McMurdo Dry Valleys, Antarctica, and dated using Atom Trap Trace Analysis (ATTA). The 81Kr radiometric ages agree with independent age estimates obtained from stratigraphic dating techniques with a mean absolute age offset of 6 +/- 2.5 ka. Our experimental methods and sampling strategy are validated by 1) 85Kr and 39Ar analyses that show the samples to be free of modern air contamination, and 2) air content measurements that show the ice did not experience gas loss. We estimate the error in the 81Kr ages due to past geomagnetic variability to be below 3 ka. We show that ice from the previous interglacial period (MIS 5e, 130-115 ka before present) can be found in abundance near the surface of Taylor Glacier. Our study paves the way for reliable radiometric dating of ancient ice in blue ice areas and margin sites where large samples are available, greatly enhancing their scientific value as archives of old ice and meteorites. At present, ATTA 81Kr analysis requires a 40-80 kg ice sample; as sample requirements continue to decrease 81Kr dating of ice cores is a future possibility.
Super!
āSome people believe a change in the level of atmospheric carbon dioxide may have played a role. That is one reason we are so anxious to find ice that will take us back further in time so we can further extend data on past carbon dioxide levels and test this hypothesis.ā
————
…test this hypothesis against computer models that will confirm the need for the UN to assume complete global control of *.*
“Some people believe a change in the level of atmospheric carbon dioxide may have played a role.”
Who are these “some people”? My guess is that they are the ones drafting a grant proposal for additional money.
Holy Batman Superman – it’s Kryptonice…!
Aw come on, someone had to do it…
Mike š
OK, OK Kryptonice…
Everyone knows Krypton 83 decays to Kryptonite.
āWhy was there a transition from a 40,000-year cycle to a 100,000-year cycle?ā Buizert said. āSome people believe a change in the level of atmospheric carbon dioxide may have played a role. That is one reason we are so anxious to find ice that will take us back further in time so we can further extend data on past carbon dioxide levels and test this hypothesis.ā Always carbon dioxide. Nothing else could possibly influence the climate on Earth. Just had to rant.
Sigh. Just once can someone do climate science without mentioning CO2?
“The ability to discover ancient ice is critical, the researchers say, because it will allow them to reconstruct the climate much farther back into Earthās history and potentially understand the mechanisms that have triggered the planet to shift into and out of ice ages.”
Critical? To whom?
āSome people believe …ā
And this is a hypothesis? Ya know, when you get there and measure the CO2 whatever it is, with this kind of thinking you WILL make a correlation- turn them upside down if they diverge; add a lag of 9,000 years; multiply it by the 18O isotope content, oh yeah and there is the models….This is a well traveled path by the hockey stick folks so it is sure fire.
And these really rare and therefore very small number of supposedly million year old 40Kg ice samples from some isolated pocket of the Antarctic will tell us what the global climate was then, but we can’t believe all the historically recorded evidence of the MWP from dozens of locations because it might not have been global?
There are just so many flaws and so many opportunities to tell whatever narrative they want to tell.
There are several different theories about the shift from 41 KA to 100+ KA glaciations, but I have never heard about CO2 level being one of them. I wonder who those “some people” are? Are they possibly fictitious, just to be able to get funds by using the magic word?
I hope they succeed, since this is definitely research that is worth continuing.
Hmmm… so many questions from a chemist who has taught General Chemistry his whole career. Krypton has six naturally occurring isotopes: Kr-78 (0.35%), Kr-80 (2.25%), Kr-82 (11.6%), Kr-83 (11.5%), Kr-84 (57.0%), and Kr-86 (17.3%). If Kr-83 is made in the upper atmosphere, then its concentration on Earth over millions of years has increased and you would have to account for this I would assume? I would also assume that all of these other isotopes are present in the sample as well which would explain the large sample size. The amount of Kr in the atmosphere is roughly 1ppm, so it would be interesting to know how much air is recovered from melting 300.kg of ice core samples. Since they say they stored it in flasks perhaps several liters of air? I would love to know how much they recovered as they do not report the volume in the paper.
Oh, jeezuss. What was the tilt of the earth then? And did it shift?
The noble gasses should give you a better ocean temperature signal than D/H ratios as they have quite nice solubility vs. water temperature curves.
“… the Presidentās 2014 Budget provides $28.4 billion in
discretionary funds for DOE {Department of Energy} to support its mission. … .”
(p. 1 (of below-cited document itself, not the .pdf file’s assigned page#))
“DOEās applied energy programs … provide the needed focus to address … { } environmental goals. The FY 2014 Budget for these applied programs includes $4.7 billion, a 42 percent increase over FY 2012 current levels… . {goals in include} “… reducing greenhouse gas emissions… .” (p. 2)
“Biological and Environmental Research ($625.3 million)
… BER research advances our understanding of the role of atmospheric, terrestrial, ocean, and subsurface interactions in determining climate dynamics to predict future climate change… .” (pp. 43-44)
Source: http://energy.gov/sites/prod/files/2013/04/f0/FY14_DOE_Budget_Highlights_Final.pdf
*$*$**$*$**$*$**$*$**$*$**$*$**$*$**$*$**$*$**$*$**$*$**$*$*
As of 5:25pm PST, April 21, 2014, the United States National Debt is over:
$17.5 TRILLION and climbing by the second… .
Source: http://www.usdebtclock.org/
*$*$**$*$**$*$**$*$**$*$**$*$**$*$**$*$**$*$**$*$**$*$**$*$*
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Research is fine.
For now, however, research such as this Krypton stuff, is a luxury we cannot afford. Once we pay down the debt to a reasonable level, THEN, we can fund stuff like this.
There are veterans making do with shoddy government medicine; there are mentally ill people willing to go into treatment, but there are not enough beds… .
In short, CO2 speculation-promoting research needs to be defunded to:
1. Pay down the debt; and
2. Put what tax money is available toward what should be much higher priorities: the real public welfare.
Maybe it had something to do with the configuration of the continents?
Fascinating, Anthony, thanks.
Dang ā¦ according to the article, it takes no less than 350kg of ice for each sample. With a typical 4″ drill core, that’s about 44 metres long (145 feet) ā¦ not quite ready for prime time ice core dating right now, but we’ll get there.
w.
Superman can finally get a date?
As Willis noted, there is no +800,000 year ice that comes in 44 metre deep sections. mms at best.
Reblogged this on gottadobetterthanthis and commented:
Absolutely cool! (Bad pun,but this really is impressive.)
I think it most impressive that they’ve needed four decades to develop techniques they knew must exist. It is good to remember that real science is hard and often quite slow.
Wow, I need to find out more about this new detector they are using.
FYI, here is some basic information. A single Kr-81 atom emits its radiation as the result of a process called electron capture, whereby a proton captures an orbital electron and the atom is immediately converted to a Br-81 atom (non-radioactive). The radiation emitted in the process is Br X-rays, so this is what the researchers have to be measuring. As noted in the article, Kr-81 is produced when a neutron strikes the nucleus of a Kr-80 molecule (2.3% of all Kr in the atmosphere). The neutron “sticks” to the Kr-80 nucleus, thereby adding a neutron to the molecule and it becomes Kr-81 (radioactive).
Man also produces Kr-81 (and a bunch of other radioactive Kr isotopes, notably Kr-85) in nuclear reactors and accelerators. KR-85 has had many industrial uses. In our atmosphere, the total amount of Kr (radioactive and non-radioactive) is 1 ppm and Kr-81 is a trace amount of that 1 ppm. I find it impressive that the researchers can capture and contain the total Kr in the ice and separate/isolate enough Kr-81 to measure. Managing any noble gas is like herding cats. With the relatively long half-life of Kr-81, you need a lot of molecules just to see a few emissions in a day. There are a ton of confounding issues when measuring low levels of this nature, but I am going to presume that the researchers’ equipment and techniques are of good quality to manage the confounding issues because Oregon has some pretty good radiation training programs. I had a bit of a chuckle at the line, “…atom trap is so sensitive that it can capture and count individual atoms” because no matter what the detection equipment, any recorded decay event is a single atom detection. It is not an incorrect statement, but it is a little misleading to the non-informed. All in all it is pretty cool that they can measure the Kr radioactive/non-radioactive ratios to get the age of something. However, remember another confounding issue with the technique – how do they know if the Kr/Kr-81ratio has not varied in the past due to different levels of neutron bombardment in the atmosphere? It normally doesn’t vary much, from what we measure in recent times, but even a slight variation will throw a timeline off.
And then there was the magical connection to CO2… Sheesh!
“Hereās something useful that works like radiocarbon dating, but on ice. Since it is cosmic ray based, it makes me wonder if it could be used to reconstruct the cosmic ray record to test Svensmarkās theory of cosmic ray modulation of climate.”
Well, neither the fluctuating solar magnetic field nor the varying cosmic ray influx would have an effect on the total amount of krypton present, just the ratio between stable krypton and the radioactive element produced by cosmic ray bombardment. Krypton-81 (2.29Ć10+5 years) and krypton-78 (1.5Ć10+21 years) are the two radioactive isotopes with a very long half life. Krypton-86, 84, 83, 82, 80 are stable. Apparently Kr-81 is produced from bombardment of any of the stable isotopes by cosmic rays.
And the authors make this big assumption:
“In the radiometric dating we make the assumption that the atmospheric 81Kr/Kr ratio has remained stable over the time period of interest.”
Presumably they mean the production of 81Kr by bombardment of Kr by cosmic rays. If that production is constant, then differences in the ratio of 81Kr/Kr are attributable to the decay of 81Kr. But if there are changes in cosmic radiation, then there are changes in the amounts of 81Kr produced relative to stable Kr. If there is an intense period of solar magnetic fields, then the amount of 81Kr relative to stable Kr is smaller for a given period of time than during a period of a quiescent sun. Ice from the first would appear to be much older than ice from the second because there is less 81Kr than in the second. So what would look like differences in the age of ice could actually be caused by differences in the rate of cosmic ray bombardment as controlled by solar magnetic fields. So you couldn’t use variation in the ratio of 81Kr/83Kr to indicate age of the ice formation unless you had some other proxy to measure changing solar magnetic fields that you could use to remove the variability in 81Kr production so that what remains would be indicative of the age of the ice alone by the 81Kr/Kr ratio.
But 14C is produced by bombardment of 14N by cosmic rays, so it changes in response to changes in solar magnetic field strength.
A couple of good links on ice core dating and issues affecting results. There is a lot more to it than just counting atoms.
http://isu.indstate.edu/jspeer/QuatEcol/Chapter5.ppt
https://journals.uair.arizona.edu/index.php/radiocarbon/article/download/1454/1458+&cd=8&hl=en&ct=clnk&gl=us
The further you go back in history (of anything on this planet), the less likely it is to have any influence on today’s planet, or any reason to know about it.
I don’t give a tinkers damn, about knowing anything about the first two rocks that stuck together, in the process of forming planet earth. and I have almost as much interest in million year old ice.
I have some 40,000 year old Kauri wood that is far more interesting. (and still in pristine condition). I couldn’t find anything made out of the 50,000 year old stuff.
Thank you, A. Grimm (7:06pm) and G. ex Sandoval (7:26pm) for that very helpful education. Illuminating! So glad you took the time to tutor us, here.
And A. Grimm, VERY good to see you again. Ever since your fine post about carbon dating (I think it was on a frozen moss thread) last autumn (I think), I’ve looked out for you. Do post more often!
Janice
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“I donāt give a tinker’s damn… .” George E. Smith.
LOL — my sentiments exactly.
Stillpraying,
Janice
Dependence between the geomagnetic field and the production of isotopes. Can see how important it is to combine the study of solar activity from the geomagnetic field strength.
http://oi58.tinypic.com/2r4sa52.jpg
Janice: (and GuarionexSandoval)
Well thank you very much, and I agree that GuarionexSandoval did a great job also. I’ve been on WUWT since about six months after Anthony started this blog, but I generally stick to my expertise of health physics (radiation safety) for postings. I used to post as “Leg” but changed to “aGrimm” a couple of years ago. I worked hard during my career to develop the skill to take the subject of radiation and put it in terms of a high school education (accounting for the too often lousy science education in our country). I’m of the mind that the interaction of radiation with matter is critical to understanding the gigantic forcing of the sun. Too few understand the basics of the interactions and clearly folks like Michael Mann don’t give a dang about understanding it. Most of the mechanisms for how radiation interacts with matter are fairly easy to learn when put in simple terms.
On the other side of the coin, the sum total of possible interactions and the permutations of which way energy will dissipate or be stored in all its forms becomes mind boggling. Contemplating it all always reminds me of how little we know. The recent WUWT post on UV & CO2 is a good example. There is nearly an infinite number of pathways that the energy of a single UV photon can dissipate or be stored in the environment. When gazillions of UV photons are involved, it is mind boggling. Additionally there are all the other photons across the whole electromagnetic spectrum and also the particulate energy forms bombarding the earth, i.e. protons, neutrons and more. We have lots of math and theories that will describe the most probable interactions and outcomes of the dissipation/storage but we cannot say for sure what a particular change, e.g. a small increase in the number of photons/particulates, will do in the big picture principally because there are just so many ways the change can be expressed. If we cannot answer that basic question, how can we answer the bigger question of what the climate might do?
If you have any questions about radiation interactions, there are a couple of folks here, like GuarionexSandoval and I, who would love to answer them.
GuarionexSandoval: thanks for expanding on the confounding factor of the rate of irradiation question I raised. Simply and well explained.
R John says:
April 21, 2014 at 3:52 pm
The amount of Kr in the atmosphere is roughly 1ppm, so it would be interesting to know how much air is recovered from melting 300.kg of ice core samples.
From: http://courses.washington.edu/proxies/GHG.pdf
Air volume at bubble closing depth is 10-15%. At a density of 0.84 kg/dm3 all bubbles are closed, which gives 40-60 liters of open volume in 350 kg ice. At that depth (~70 m), pressure of the ice layer is about 6 bar, which gives a volume of 240-360 liter air at normal pressure. Quite a lot, but still needed to find the one needle in the haystack…
Anyway a extremely good example of the progress in analytic techniques!
Perhaps I can give folks here a simple understanding of some the complexities involved in low level radiation counting, such as what is being done by the Oregon Kr-81 researchers.
First is understanding the half-life of the radionuclide. For ease of imagining, I am using only 10 atoms in all the examples. We use a very imprecise rule of thumb in which we say that within 10 half-lives all the atoms will decay. Therefore, Kr-94 has a 1.4 second half-life nuclide so within 14 seconds (roughly) all ten atoms will emit, which is called decay, their radiation. This is quick to measure. Kr-89 has a 3.2 minute half-life, so it is about 32 minutes to measure all ten decays. Still quick to measure. Kr-85 has a 10.8 year half-life. Statistically it will take 108 years to see all ten atoms decay – an average of one decay per decade. With the 210,000 year half-life for Kr-81, it will take 2,100,000 years for all ten atoms to decay*. Hmmm, I doubt I will be around to see all the Kr-81 decay. Now ten atoms are darn few atoms, but the point is: for us to be able to measure long half-life nuclides in a reasonable time, it takes a lot more atoms of a long-lived radionuclide than it does for short half-life nuclide. I really wonder how many atoms the Oregon folks extract from trapped air bubbles in ice, and its being a noble gas that may not stay put in a trapped gas bubble there is the question of accuracy across a long time span. Hopefully they have addressed these issues. (*theoretically all ten could decay in one day, but statistically it will take this long.)
Beta, neutron and alpha emitters are a whole ‘nother ball game of detection, so I am focusing on the gamma/X-ray emission that the Oregon folks are looking at.
The next issue is background radiation. Radiation is everywhere and just about in everything. If the measuring equipment cannot shield the background radiation and is not sensitive enough to discriminate between radiation levels, then do not plan on counting low levels of radiation.
Energy resolution is the ability of the detector to discriminate between different energy levels. All radionuclides emit their gamma/X-ray radiation at discreet energy levels, but there are plenty of nuclides that emit at the same or very close level. As an example, if the nuclide of interest emits gamma/X-ray radiation at 120 KeV, but another interfering nuclide emits at 122 KeV, then the interfering nuclide would likely overlap into the 120KeV area and mess up the results. Scintillation detectors are not very good at resolution. Germanium detectors are considerably better and used a lot in low-level counting, but can still have resolution problems. However, NIST has been working on a detector that is exquisitely capable of separating spectral energies, so I am wondering if the Oregon detector is something along these lines.
Then there is the question of how well the detector can detect the energy of interest. Different detectors or designs of detectors may or may not see all of the energy of interest. Gamma/X-ray photons are penetrative, and just like light through a white sheet of paper, not all of the radiation will be stopped and measured. How much of the radiation the detector can measure is called its efficiency. My sweetie of a germanium detector, with its high resolution ability, may only be in the 1-2% efficiency range for an energy level. Typically the better the detector’s resolution, the less efficient it is. Therefore you either need more atoms or longer counting times to get reasonable results because you are seeing only a small proportion of the decays. It is a question I have about Oregon’s detector – what is its efficiency for the energy of Kr-81.
The detectors’ electronics usually have some “noise” in the circuits. Today’s circuits are pretty darn good and manufacturers build in algorithms that correct for the noise. However, it is an area to which the researcher needs to pay attention when doing low level counting.
Another problem often overlooked by researchers is cross-contamination. I solved more than one researchers’ problems by teaching contamination control techniques – essentially: behave like a medical doctor trying to prevent bio-contamination; and don’t trust fellow workers to touch your research because they may not be as meticulous as you. A noble gas like Kr-81 poses airborne cross-contamination problems. Usually good air handling systems solve that problem.
Judging from the article, the method for Kr-81 extraction/collection sounds very complex with the associated potential for problems in any complex system. I hope the Oregon researchers have a good handle on this and do fault analysis and checking.
Radiation detection methods, and issues, is easily a semester course and more when it comes to low-level counting. I just hope this gives you folks some idea of the potential problems.
PS: the only difference between a gamma and X-ray emission of the same energy is where they originated from: a gamma originates in the nucleus, and an X-ray originates in the electron shell. Normal detectors cannot tell where the emission came from but it doesn’t matter.
How did they know it was 120,000 year old ice in the first place to identify it ‘correctly’.
Just how much Kr is in the atmosphere in the first place to get trapped in ice so that the can count the decaying isotopes.
It all sounds ‘well dodgy’ to me.
Retirement: the place you go to not keep up on developments in your field. Dang you Anthony, you forced me into keeping up! I said I wanted to look into the ATTA detector, so I did.
The ATTA detector does not use radioactive decay as the measuring mechanism, therefore much in my previous post does not apply. Using liquid Xenon, lasers and Doppler shift, it is pretty amazing in that they can trap and identify a single Krypton atom from a very low (10 e-13) abundance of the stuff. Apparently the detector was initially developed to help alleviate a problem they were having in looking for neutrinos using liquid Xenon. The problem is that Krypton remains as a contaminant in highly purified liquid Xenon and with Kr’s numerous radioactive isotopes, especially Kr-85, the decay from the radionuclides would give false information to the standard radiation detectors trying to measure neutrino interactions. The ATTA detector can determine the amount of Kr contamination in the Xe. Therefore, introducing extra Kr to the Xe, such as Kr extracted from ground water or ice samples, the amount of Kr can be measured in the ATTA.
I have a ways to go yet to be able to explain it in simple terms and I am still a little confused about some aspects of the system, but I hope the above helps.
Thanks Willis, I was about to post a question along similar lines (how big a core is 350kg of ice) and i see you anticipated my question. They do say they “think” they can get it down to a 20kg sample, but that is still 10-15 ft of core and I wonder how long a period of time that represents? This won’t give you much in the way of resolution….
Rob says:
April 22, 2014 at 7:27 am
For a 20 kg sample, that would be a 2.5 meter core length.
If you look at the ice depth – age of the Dome Concordia (Dome C) ice core, the lowest meters give some 2000 years per meter at near 800 kyr of age, or 5 kyr for a 2.5 m sample or within 0.6%. For older/deeper cores it may be more, as there is more pressure and/or more flow over time, but even so, if they can bring it down to 20 kg, they can detect how old the ice is within a few % of the age, which is good enough for a search of the oldest ice on earth…
See:
ftp://ftp.ncdc.noaa.gov/pub/data/paleo/icecore/antarctica/epica_domec/edc3deuttemp2007.txt
for the depth – ice age – dD data of the Dome C ice core.
aGrimm, Sandoval: Excellent contributions. One correction, though. Carbon “radiometric” dating is no longer performed by measuring decays – where you have to wait about 10,000 years on average for a spontaneous decay of one atom of C14. With 10,000 atoms of C14 in your sample, it would be 1 year, with 3,650,000 it is one day. Now we use mass spectrometry and measure the mass of atoms directly without having to wait for a decay. The analysis is done in hours and the sample only needs to contain several C14 atoms.
The assumption of a constant Kr81/Kr83 ratio is likely incorrect. The same assumption was originally made for C14/C12 ratio, and was proven incorrect with analysis of material dated by tree rings. Finally, the article is extremely vague regarding how Kr81 is produced.
Looks like they could refine their analysis technique by searching for pee in Portland water supplies. Somebody call the Portland water manager.
I was reading this and thinking how odd, some real and interesting science from Oregon State University. But then I got to the bit about CO2 causing the MPR and found it strangely reassuring – this is the OSU that we know.
The MPR singifies a trend of deepening glaciation. This interglacial may be the last.
Thank you, A. Grimm, for MORE great teaching. You should write a main post for WUWT!
In the hopes that others may see this and take the time to read your post carefully:
Key Points Summary of A. Grimm (2:51am and 4:57am):
1. Half-life of the Radionuclide
“With the 210,000 year half-life for Kr-81, it will take 2,100,000 years for all ten atoms to decay*. …”
2. Background Radiation
“If the measuring equipment cannot shield the background radiation and is not sensitive enough to discriminate between radiation levels, then do not plan on counting low levels of radiation.”
3. Detector Resolution v. Efficiency
“… the better the detectorās resolution, the less efficient it is. Therefore you either need more atoms or longer counting times to get reasonable results … .”
A. Grimm at 2:51am above.
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4. ATTA Detector May Surmount Some of the Above Difficulties
” *** The ATTA detector can determine the amount of Kr contamination in the Xe. ***”
A. Grimm at 4:57am above.
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Please do not ever completely “retire”! We need you.
Gratefully,
Janice
P.S. And, (re: 12:11am) you’re welcome! #(:))
What’s not to like? Argonne on Krypton…
(sorry, an ignoble pun on noble gasses…)
This paper is a rich source of information and speculation on the on the MPR and timing of interglacials in general:
http://andy.seao2.info/pubs/manuscript_maslin_and_ridgwell.pdf
While an authoritative discussion of interglacial timing, it is remarkable how solidly the authors are locked into the paradigm of CO2 forcing temperatures. All their mechanistic suggestions concerning a forcing role of CO2 on temperature are equally valid in the exactly reversed paradigm – temperatures forcing CO2, and their failure to see or acknowledge this is surprising. Even the CO2 feedback that they propose could just as easily be albedo feedback. All that they dare admit is that the reasons for changes in CO2 level are poorly understood.
None-the-less a worthwhile read.
I wonder if they’re serious about CO2 as a possible factor in the switch from 40,000 to 100,000 year periodicity in the glacial/interglacial cycle. Since both periods are related to orbital mechanics, IMO the main reason for looking for a terrestrial cause would be funding rather than evidence.
It’s depressing to see my brother’s & parents’ alma mater get on the CACA gravy train in this way, but I guess researchers today have little choice. Still, this is closer to real science than most CACA-corrupted papers.
“””āThe international scientific community is really interested in exploring for old ice in both types of places and this new dating will really help,ā Brook said. āThere are places where meteorites originating from Mars have been pushed out by glaciers and collect at the margins. Some have been on Earth for a million years or more, so the ice in these spots may be that old as well.ā
Buizert said reconstructing the Earthās climate back to 1.5 million years is important because a shift in the frequency of ice ages took place in what is known as the Middle Pleistocene transition. The Earth is thought to have shifted in and out of ice ages every 100,000 years or so during the past 800,000 years, but there is evidence that such a shift took place every 40,000 years prior to that time.”””
Meteorites from Mars of a million years or more old and a change in the periodicity of ice ages..
Interstellar background around the heliosphere bubble must have been messier..
There is still so much that we don’t yet know about the Galactic, Solar and Anomalous cosmic rays that bombard earths upper atmosphere. Polar regions yep good place to find them..
3 Doors Down
Kryptonite
I took a walk around the world
To ease my troubled mind
I left my body lying somewhere
In the sands of time…
I see WUWT has another Cosmic Ray topic, that does not mention the role of ACR..
Svensmarkās Cosmic Theory and Cloud Cover Depictions in Little Ice Age Art.
Well, P. Frisch has an article or two published dealing with ACR and a few theories about why the deviation in C14 and Be10 of the GCR records.. Headed for the new Cosmic Ray topic..
Hope Dr. S. checks in there ..