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 Myr is beyond the reach of 14C-dating.
From Oregon State University CORVALLIS, Ore. – A team of scientists has successfully identified the age of 120,000-year-old Antarctic ice using radiometric krypton dating – 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 – which has constant and well-known decay rates – 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: 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.
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Super!
“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.”
————
…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 🙂
OK, OK Kryptonice…
Everyone knows Krypton 83 decays to Kryptonite.
“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.” 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 Earth’s history and potentially understand the mechanisms that have triggered the planet to shift into and out of ice ages.”
Critical? To whom?
“Some people believe …”
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 President’s 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#))
“DOE’s 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 … 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) … 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!
“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.”
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 (2.29×10+5 years) and krypton-78 (1.5×10+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.