Antarctic Ice Cores: The Sample Rate Problem

 

Guest Post by David Middleton

In my first guest post (CO2: Ice Cores vs. Plant Stomata), we discussed the merits of ice cores vs. plant stomata as paleo-CO2 measurements. One of the key stomata papers I cited was Thomas van Hoof’s “Atmospheric CO2 during the 13th century AD: reconciliation of data from ice core measurements and stomatal frequency analysis.” Van Hoof and his coauthors demonstrated that the Antarctic ice cores only reflected the low-frequency component of the CO2 “signal”…

It is well known that diffusion processes within the firn layer and the gradual enclosure of the air in the lock-in-zone of the ice lead to a reduced signal of the original atmospheric variability and may obscure high-frequency variations (e.g. Trudinger et al., 2003).

This “diffusion process” is primarily a function of snow accumulation rate. The higher the accumulation rate, the less diffusion and the higher frequency resolution. Compaction effects due to burial can also add to the diffusion process. Dr. Van Hoof’s paper presented strong correlative evidence that the plant stomata chronologies were capable of recording a much higher frequency CO2 signal than the ice cores.  I was curious about whether or not any evidence of the diffusion effect on CO2 resolution could be identified in the ice cores through the correlation of CO2 mixing ratios and snow accumulation rates.  NOAA’s paleoclimatology library does not include any accumulation rate data for Antarctic ice cores with published CO2 chronologies; but the accumulation rate can by approximated by calculating a sample rate.

I used data from two Antarctic ice cores (Law and Taylor Domes) over most of the Holocene (11 kya to the early 20th century) to compare the sample rate to the CO2 mixing ratio. The sample rates were calculated by simply dividing the sample depth interval by the ice age interval:

sr = [(zn – zn+1) / (tn – tn+1)]

Where sr = sample rate (m/yr), z = sample depth (m) and t = ice age (yr)

I then plotted the CO2 mixing ratio against the sample rate.  Not surprisingly, there is an extremely strong correlation between the sample rate and the CO2 mixing ratio throughout the Holocene…

Fig. 1) Antarctic Ice Cores: Sample rate vs. CO2 during the Holocene.

This makes it very clear that the low CO2 values in the Antarctic ice cores during the Holocene could easily be the result of diffusion and do not constitute valid evidence of a stable pre-industrial atmospheric CO2 level of ~275 ppmv.

References

Etheridge, D.M., L.P. Steele, R.L. Langenfelds, R.J. Francey, J.-M. Barnola, and V.I. Morgan. 1996.  Natural and anthropogenic changes in atmospheric CO2 over the last 1000 years from air in Antarctic ice and firn. Journal of Geophysical Research 101:4115-4128.

Indermühle A., T.F. Stocker, F. Joos, H. Fischer, H.J. Smith, M. Wahlen, B. Deck, D. Mastroianni, J. Tschumi, T. Blunier, R. Meyer, B. Stauffer, 1999, Holocene carbon-cycle dynamics based on CO2 trapped in ice at Taylor Dome, Antarctica. Nature 398, 121-126.

Van Hoof, T.B., K.A. Kaspers, F. Wagner, R.S.W. van de Wal, W. Kürchner, H. Vissher, 2005. Atmospheric CO2 during the 13th century AD: reconciliation of data from ice core measurements and stomatal frequency analysis. Tellus (2005), 57B, 351–355.

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113 thoughts on “Antarctic Ice Cores: The Sample Rate Problem

  1. Wouldn’t diffusion be easy enough to measure in a laboratory environment? I can see using a press and snow in a container with sides made of a gas-permeable substance. Slowly compact 10 feet of snow and measure CO2 in the cores after a certain amount of time to see if its an accurate representation of atmospheric CO2 one year ago.

  2. Prezakly. There is little or no chance that spikes would be preserved. And the baseline error is necessarily downward.

  3. First – I’m not sure I understand ‘sampling rate’. Is this a proxy for the thickness of the annual ice layers? On the subject of diffusion, I understand you are talking about movement of CO2 in as-yet porous, unconsoldidated ice over multi decades. As a Precambrian geologist, I’m familiar with a much more aggressive form of diffusion – that of elements, like K, Na, Si, Al, etc. through solid rock! For example, a sequence of pillow lavas (when lava erupts on the ocean floor it shoots out soft ‘toffee blobs’ into the seawater that pile up layer-upon-layer) of basaltic composition (black Mg-Fe silicates) of Archean Age in the Lake of the Woods area of Manitoba-Ontario have been partly altered from the pillow edges inwards to a more granitic composition (grey-pink coloration) by diffusion of alkali-alumina-silica solutions that replace the pre-existing material but preserve the pillow structure. A more familiar example is fossilized wood where entire tree trunks have been replaced by silicates with no trace of the original wood. Even dinosaur bones are no longer of the original calcium phospate composition but rather have been replaced by (I believe – I’m not a paleontologist) silicate material. Regarding the ice cores, I have always believed that the relativel uniformity of CO2 is due to the more aggressive form of diffusion along crystal boundaries driven by high pressure. Moreover, one of the characteristics of the ‘invading’ solution is its reactivity with the solid medium and CO2 does react with H2O.

    Any geochemists out there? I hate to wake up the ‘Granitizationists’ like Doris Reynolds (1899 -1985) whom I met at Bedford College, London in the 1960s -are there are any of you left these days who believe all rocks are formed by pervasive diffusion of a endless soup of mobile elements? Now is the time to be helpful.

    http://www.britannica.com/EBchecked/topic/241716/granitization

  4. Piers Corbyn says “you aint seen nothing yet”. This guy can save lots of lives and keep us much safer that the current crop of forcasters.

  5. Just a casual thought — ice is an unusual solid being less dense than liquid water — I wonder if ice might be slightly CO2 repulsive such that the CO2 concentrations observed in deep ancient ice could actually tend to be less than the average of the CO2 concentrations when freshly formed … Does anyone know?

  6. Spector;
    Don’t think so, but the bubbles have a thin cold-water “pressure” film, and cold water aggressively dissolves CO2. IMO, that would tend to transport it out of there.

  7. For a view from the other side I recently came across this article:

    http://www.sciencedaily.com/releases/2009/10/091008152242.htm

    She says her method of determining CO2 levels by looking at the ratio of calcium/boron in marine algae corresponds well with the ice core records.

    I emailed her recently regarding what I consider to be some errors or flaws in her statements/reasoning, but, if I receive a response, I wouldn’t post any such correspondence without her permission.

  8. Is the pattern of CO2 concentration versus depth/age the same in other ice cores? Does the CO2 level out at the same concentration? Is this what the warmers are relying on as evidence of a lower and stable pre-industrial CO2 concentration?

    Maybe there is another explanation. What about biological processes? Is there any cyanobacteria which is photosynthesizing in the firn zone? Or maybe something to do with phase changes from gas to liquid and back to gas during burial/compression and sampling/decompression?

  9. Spector says:
    January 1, 2011 at 6:10 pm

    Yes. The experiment, CO2 diffusion in ice, has been performed at Scripps in 2008, demonstrating unequivocally that CO2 does indeed diffuse through ice at a rate that would be significant over years or decades timeframe, much less millenia or megayears, and initial concentrations will decrease if they are higher than the current ambient concentrations:

    CO2 diffusion in polar ice : observations from naturally formed CO2 spikes in the Siple Dome (Antarctica) ice core
    Auteur(s) / Author(s)
    AHN Jinho (1 2) ; HEADLY Melissa (1) ; WAHLEN Martin (1) ; BROOK Edward J. (2) ; MAYEWSKI Paul A. (3) ; TAYLOR Kendrick C. (4)

    Journal of Glaciology ISSN 0022-1430 CODEN JOGLAO
    Source / Source
    2008, vol. 54, no187, pp. 685-695 [11 page(s) (article)] (1 p.1/2)”

    I had been posting about CO2 diffusion for some time at WUWT and elsewhere, but nobody has put together what this means, until now, to my knowledge. Fick’s Laws of diffusion govern diffusion of gases and solids in gases liquids and solids. The Second Law states that diffusion occurs from high to low concentration, and is directly proportional to change of initial concentration, and inversely with time.

    What this means is that 600 ppm in a bubble in ice with 300 ppm outside will deplete CO2 in the bubble until the outside concentration approaching 300 ppm is asymptotically reached. A concentration of 1200 ppm will diffuse twice as fast as 600, 2400 ppm 4 times as fast, etc. Twice the age, conversely, will have twice the time for diffusion, so old cores will be nearer outside equilibrium level.

    Practically, then, no old ice core can give an accurate result for ancient conditions using the traditional CO2 bubble gas chromatography method, and the result will be worse the higher the initial concentration of CO2 that existed in the past, and even worse the longer the residence time in the core. Old, high CO2 cores will be nowhere near the initial condition. So if we had tens of thousands of CO2 ppm in the past, ice core CO2 methodology would never show it.

    This is intuitively obvious to me, since the extreme size of dinosaurs 100 Mya required high CO2, parts per thousand, for plants to grow to supply them with food,; said plants could then generate the high oxygen levels the dinosaurs needed to maintain their metabolism at such high levels.

    I would think that the leaf stomata method, since it is static and not dynamic as is the CO2 sampling method, should be the method of choice until a better proxy comes along. Moreover, the CO2 method should be discarded completely for anything but current atmospheric conditions.

    One cannot deduce a past static state using a dynamic conditions method.

  10. Gary Pearse is correct to be skeptical about the fidelity of gas-bubble contents in millenial ice to the atmosphere at the time of inclusion. Honestly, can anyone really believe that atmosphere entrained among snow crystals during snowfall will remain unchanged for hundreds/thousands of years while those snow crystals slowly get transformed to firn and then to ice (multiple H20 phase changes)?

    Oxygen isotopes in the ice are not such a problem because the water molocules remain the same in ice (regardless of transformations). CO2 as a trace contaminant in the gas phase of the ice-air mixture is much more susceptible to diffusion/conduction/convection processes that would tend to smooth out “spikey” variations over time.

    I think CO2 concentration values in ice core are largely meaningless due to thermodynamic “smoothing” issues (above).

    Modern CO2 concentration values in the atmosphere are largely governed by ocean heat content and biologic uptake/decay.

    Human effects on CO2 are trivial and mostly immaterial regarding “global temperatures”, whatever they may be. Humans greatest effect on atmospheric temperatures is in “urban heat islands” due to land-use changes.

    But not enough to create any “global” changes, except in unrealistic computer models of “climate change”.

  11. Ah, Dave…I just looked at the Law Dome data ( ftp://ftp.ncdc.noaa.gov/pub/data/paleo/icecore/antarctica/law/law_co2.txt ) and I notice a little bit of a pattern in time…like the only data above 300 ppm is that dated after 1900 and, in fact, the data is not a scattering of points centered around a higher value…It is simply the march of CO2 levels upward in the last 100 years or so. The plot that you made completely obscures the very strong, steady dependence of the CO2 level on the mean air age in the Law Dome data! Since the Taylor core has such a low accumulation rate, it doesn’t have any data points in the post-industrial era!

    I know you really really want to prove your incorrect preconceptions but this post is frankly ridiculous!

  12. Jim Cole says:
    January 1, 2011 at 7:21 pm

    Hear, hear!

    Well said. Anyone that has ever thought that CO2 can be “trapped” in ice is not appreciating molecular movement and thermodynamics.

  13. OT
    I musing a little bit, please indulge me.

    We could end all this anti-constitution talk with just one nuke exploding somewhere in the world. All markets would crash and these constitution haters will come running back to mama constitution in a New York minute when they start getting cracked on the head by Homeland Security’s jack booted thugs soon thereafter.

    The complete and total economic collapse of the USA is a bit more subtle, but has an absolute certainty of 100% happening. No one is sure of the timetable except those who really pull the strings. How much longer can the Federal Reserve kick the can down the road? By May 2011 we will need an answer. QE3, Yes? If No we got 6 months, if yes, six months more, tops till, May 2012, notwithstanding a collapse of Europe happening before, then all bets are off. The markets will front run the collapse. They seem to be starting to do that already. Buy Silver and Gold.

    Either way, we should all be uniting to get the Jack Booted Thug of Homeland Security out of our lives before the inevitable happens. I’d prefer to see The Department of Homeland Security abolished now.

  14. bubbagyro says:

    Yes. The experiment, CO2 diffusion in ice, has been performed at Scripps in 2008, demonstrating unequivocally that CO2 does indeed diffuse through ice at a rate that would be significant over years or decades timeframe, much less millenia or megayears, and initial concentrations will decrease if they are higher than the current ambient concentrations:

    “CO2 diffusion in polar ice : observations from naturally formed CO2 spikes in the Siple Dome (Antarctica) ice core
    Auteur(s) / Author(s)
    AHN Jinho (1 2) ; HEADLY Melissa (1) ; WAHLEN Martin (1) ; BROOK Edward J. (2) ; MAYEWSKI Paul A. (3) ; TAYLOR Kendrick C. (4)

    Journal of Glaciology ISSN 0022-1430 CODEN JOGLAO
    Source / Source
    2008, vol. 54, no187, pp. 685-695 [11 page(s) (article)] (1 p.1/2)”

    Here’s a copy of that paper, so that we are all on the same page: http://ns.geocraft.com/WVFossils/Reference_Docs/CO2_diffusion_in_polar_ice_2008.pdf Reading that paper does not seem to lead to the conclusions you draw. In particular, they note:

    (1) “Smoothing of the CO2 record by diffusion is one to two orders of magnitude smaller than the smoothing by diffusion in the firn at the depth of 287m (gas age = 2.74 kyr BP) in the Siple Dome ice, and so does not degrade the record.”

    (2) At depths where the ice age is tens of thousands of years (they use 80,000 years as an example), the diffusion may be comparable to the diffusion in firn and hence it may have “an impact on the smoothing of CO2 records on a decadal scale”. However, they admit that “there are no decadal CO2 data for
    ice that is 80 kyr old”. Hence, it would seem that their conclusion about smoothing is, at least at the moment, basically academic.

    (3) They also note factors that make the diffusion less of an issue for other ice cores: “Ice cores from colder sites than Siple Dome would experience slower CO2 diffusion in deep ice. The formation of clathrate ice (bubble-free ice) at depths from 500 to 1200m (25–65 kyr) at other Antarctic cold-drilling sites (Vostok, Dome Fuji and EPICA Dome C) is expected to result in highly reduced gas diffusion (Salamatin and others, 1998).”

    Perhaps your misreading of the paper stems from the fact that you are reversing how the timescales work. You seem to think their talk about what happens on years to decades mean much more diffusion will happen over longer times. However, what they are doing is looking at 80,000 year old ice and saying, “The amount of diffusion in this ice might be enough for the CO2 to migrate enough to smooth out the CO2 data over a time period of years to a decade or so.” Do you understand the difference?

  15. OT
    Something that has always puzzled me about the US Civil War. It seems to highly organized to have not been staged? We fell for the Civil War. Everything the Civil War accomplished could have been accomplished by legislation. Every other country in the world did it that way. What else won’t we fall for? I count 33% of the population woken up in recent years. I wouldn’t worry yourself too much about it. It only took 8% of the population of the US in 1776 to beat the British and win us a country. And what a great country.

    “What a Country!” TV Spot from WPIX-11

  16. Gary Pearse – look for granitisation processes in

    http://www.ellistonresearch.com.au/Verification%20Reports.pdf

    This is yet another example of experts looking down long noses at an emergent theory, without being able to answer the awkward questions posed to the mainstram hypotheses. Theory developed with Prof S Warren Carey, a giant among geologists, also shunned by the establisment (until they found him likely to be correct about plate tectonics).

    Then if you are so inclined, read about ice/gas age gaps at

    http://homepage.ntlworld.com/jdrake/Questioning_Climate/_sgg/m5m1_1.htm

  17. The World Wide Web took over the vastness of the US Empire years ago. When are they going to see that?

  18. Spector says: January 1, 2011 at 6:10 pm – “Does anyone know?”

    Short answer, no.

    First one has to assume that isotope fractionation happened, with the common explanation being that ocean evaporation leaves behind some heavier isotopes. That’s ok, sort of. Then you make a quantitative relationship (which is really not ok, sort of loose).

    Then you have to assume that these isotopically anomalous air packets find their way over the miles of ice to sites like Vostok and the South Pole, which are very cold and very dry. Snow seldom forms. (Expressed as “low accumulation rate”). It’s plausible, from watching movies of the strong winds at these places, that what accumulates also includes windblown ice particles of unknown isotopic history or origin. Next, you assign your isotopic temperature reconstruction to the location of the ice core, rather than the postulated ocean evaporation source a thousand or more miles away, ignoring the stong wind mixing effect.

    Then you have to get your time line right, which raises awkward questions. If the Vostok hole, estimated older than 700,000 years, is deepened until there is no longer ice (but a lake or rock) – then what was the climate like 700,000 years ago before the ice was put in place? Some say the older ice was squeezed sideways into the oceans, but I think they are having a guess. If so, they are returning the isotopically anamlous ice back to the sea, so we have the makings of a mixed system where present day isotopic fractionation figures are partially determined by the amount of ice remelted to the oceans.

    It is amusing to work through the convolutions of logic (often without the benefit of measurement or experiment) that are created to explain the awkward.

    There is a lot of prior discussion on this blog and on CA. More questions than answers.

  19. Interesting info on the Thorium fuel. Needs more advertising and pushing, I feel, especially with the woodentops in parliament.

    .

    Archie, could you also do an analysis of hydrogen as a ‘fuel’. We have a mayor of London and several influential parliamentarians who think that hydrogen is the way forward. I have been trying to tell them for some time that:

    a. Hydrogen is not a fuel, it is a ‘battery’, an energy storage medium. And since the original fuel source is mostly coal and oil, hydrogen is effectively a fossil fuel.

    b. Hydrogen is perhaps the most inefficient ‘battery’ we have. I estimate the losses being so great, that a hydrogen-fuelled car will do just 1/3 the mpg of a traditional fossil-fuelled car.

    These truths need to be broadcast widely in the media, as there is a body of opinion that is pushing us towards hydrogen as a ‘fuel’. In reports recently I saw Boeing, GM and BMW all pushing the lie that hydrogen is ‘100% clean, with only water from the exhaust’ – while quietly ignoring the fact that the electricity to create the hydrogen was fossil fuelled.

    There is also a chemical process that generates hydrogen through a reduction process, but again the true fuel for this process is oil. But again the calculations that I made on this process – after you have liquified the hydrogen, stored it, and then passed it back through a fuel cell – showed that it was less than half as efficient as a diesel car or truck. In other words, the ‘clean hydrogen’ actually emits twice the CO2 and noxious gasses as a standard diesel car. Plus, the added complexities and equipment mean the fuel will be four times the cost.

    Thanks.

  20. RE: bubbagyro January 1, 2011 at 6:56 pm –

    What this means is that 600 ppm in a bubble in ice with 300 ppm outside will deplete CO2 in the bubble until the outside concentration approaching 300 ppm is asymptotically reached.

    But, what about a 300 ppm bubble forming in an atmosphere of 600 ppm? The comment is silent on this point.

    Should we expect the behavior to by symetric? There are forces that argue against symetry.

    First, there is size and mass of of the CO2 molecule compared to N2 and O2. During compression and closing of the bubble, the molecular sieve effects could be come important in a Physical sense. Second, the Chemical effects of solubility at the ice crystal surface during forming of the ice bubble may enhance or counter act the physical molecular sieve.

    Third, what about the snow_to_ice accumulation rates with a 300 ppm bubble in a 600 ppm atmosphere versus a 600 ppm bubble in a 300 ppm atmosphere? Does anyone believe they are the same? Up to a couple of years ago, IPCC would certainly propose much less snow in a 600 ppm environment (dare we say “none”) than a 300 ppm atmosphere. Today, with England snow covered and Ireland’s water pipes bursting, it would not surprise me if they suddenly claim more snow at 600 ppm than at 300 ppm – somehow. I guess the IPCC would say the matter is only academic because according the the ice cores, [CO2] has never been as high as 600 ppm and the physical inability of ice to preserve 600 ppm spikes in a 300 ppm average is unproven. But an experiment showing this inability might be easy and inexpensive to perform.

    Fourth, to the suggestion of an experiment that snow should be compressed into ice to analyze the potential diffusion. The compression by mechanical means would tell us very little. It has to be compression by snow accumulation. So you can start off with a steady accumulation of snow, but very the atmosphere in [CO2] over time and see if the forced [CO2] is preserved in the bubbles. Rate of accumulation would be a critical variable: could a 1 yr test represent a 100 year natural accumulation?

    While it could be done, more rigorous tests would be to vary the atmosphere above the snow in temperature and pressure as you accumulate snow. In the course of forming an ice bubble (50 to 500 years) the atmospheric pressure possibly changes by at least 20 mbar weekly from weather systems. That would be 2500 to 25000 kneadings of the entire firn gas column as the column is degassing during compression. It is not much of a pressure change, but repeated thousands of times during the formation of the ice bubbles, is it insignificant factor in the bubble’s composition?

  21. bubbagyro says: January 1, 2011 at 6:56 pm

    Yes. The experiment, CO2 diffusion in ice, has been performed at Scripps in 2008, demonstrating unequivocally that CO2 does indeed diffuse through ice at a rate that would be significant over years or decades timeframe, much less millenia or megayears, and initial concentrations will decrease if they are higher than the current ambient concentrations:

    I think you are slightly mis-interpreting the results. The abstract states

    Smoothing of the CO2 record by diffusion at this depth/age is one or two orders of magnitude smaller than the smoothing in the firn. However, simulations for depths of 930–950m (60–70 kyr) indicate that smoothing of the CO2 record by diffusion in deep ice is comparable to smoothing in the firn.

    That seems to state that the diffusion is about as significant as smoothing when the ice originally compacts. So for recent ice, the effect is small. For moderately old ice, the effect is predicted to be similar to other smoothing. For really old ice, the smoothing presumable would be more than the smoothing due to compaction (which I have typically heard to be about 100 years). So it is quite possible that the oldest ice samples are smoothed over 1000 years or so. But that still gives some very useful data.

  22. This seems to me to be another classic case of experts in one discipline not consulting wide enuf with other disciplines. The issues over at CA demonstrate the folly of not using the correct statistical methods, and O’Donnell et al demonstrate the problems of geophysicists likewise not consulting with statiticians. I was originally a physical chemist, and the issue of ice core veracity has always troubled me.

    I guess my question is why don’t these ice core people talk to the physical chemistry people.

  23. Nigel Calder in ‘Magic Universe’ (Oxford, 2003 pages 110-112) describes the mismatch between ice-core CO2 concentration and that revealed by stomata/cm2 in preserved birch leaves. The leaves can form well definined annual layers over thousands of years. The stomata count is itself digital, so even partially decayed leaves yield useful information (unlike CO2 level in ice bubbles, subject as that is to diffusion etc).
    This work was dismissed by the IPCC because it “conflicted with the ice-core data”.

  24. This is not explained very well.

    Is David proposing that CO2 is being removed from the snow by diffusion but N2 and O2 do not diffuse out of the snow thereby altering the ratio?

    I am going to make a wild guess that the relative diffusion rates of gasses in ice are known. So what are they. My intuition says that CO2 would be slower as the molecule is bigger and this is the opposite if what is leopard.

  25. bubbagyro says
    ————
    This is intuitively obvious to me, since the extreme size of dinosaurs 100 Mya required high CO2, parts per thousand, for plants to grow to supply them with food,; said plants could then generate the high oxygen levels the dinosaurs needed to maintain their metabolism at such high levels
    ————
    There would never be enough CO2 in the air to allow photosynthesis to ellevate O2 by a significant amount.

  26. bubbagyro says
    ———

    What this means is that 600 ppm in a bubble in ice with 300 ppm outside will deplete CO2 in the bubble until the outside concentration approaching 300 ppm is asymptotically reached. A concentration of 1200 ppm will diffuse twice as fast as 600, 2400 ppm 4 times as fast, etc. Twice the age, conversely, will have twice the time for diffusion, so old cores will be nearer outside equilibrium level.
    —————
    this is relevant but it ignores an important factor: the continuously increasing depth of snow. This increases the diffusion length and makes interchange with the atmosphere slower..

  27. An interesting consequence of the ‘diffusion’ theory is that it could explain/be used to explain why CO2 rises lag temperature increases.

    After all, diffusion in the ice core context should theoretically be skewed towards newer layers as opposed to older, more solidly frozen and compacted layers.

  28. Michael [January 1, 2011 at 6:00 pm] says:
    Michael [January 1, 2011 at 8:13 pm] says:
    Michael [January 1, 2011 at 8:38 pm] says:
    Michael [January 1, 2011 at 9:05 pm] says:

    OFF-Topic: Hey Michael, are you still celebrating New Years, or are you just testing the moderators?

    ON-Topic: Has anyone ever heard of any discoveries of pristine air samples perhaps trapped in a bubble inside an amber sample or some other well-preserved ancient compound? It seems to me that this may actually be possible. I know this is true because I saw it in Jurassic Park.

    Another thing I have wondered about is whether anyone has tried to measure CO2 from *new* 5 or 10 year old ice in both the arctic and antarctic. This could be measured by a trusted scientist and then compared to recent CO2 samples from Hawaii. They had better match up or else, Houston, we’ve got a problem.

    What do ya’ll think?

  29. Gary Pearse says:
    January 1, 2011 at 5:59 pm (Edit)
    First – I’m not sure I understand ‘sampling rate’. Is this a proxy for the thickness of the annual ice layers?

    […]

    The layers aren’t annual per se. The sample rate is a proxy for snow/ice accumulation rate and compaction. These are both rather shallow cores (Talyor Dome 357 m, Law Dome 535 m). So the compaction effects should be very minor relative to the accumulation rates and would likely be very similar in the two cores. The vastly different accumulation rates would dominate the sample rate calculation as it pertains to resolution.

    In the DE08 ice core from Law Dome, the depth interval from 83.1 m down to 197.55 m represents 100 years (1839-1939) of ice column. The average sample rate over that interval is 1.14 m/yr.

    In the Taylor dome ice core, the comparable depth interval (86.75 m to 185.925 m) represents 2063 years (631 BC to 1560 AD) of ice column. The average sample rate over that interval is 0.05 m/yr.

    The sample rate of Law Dome is more than 20 times that of Taylor Dome. Anyone who has aver processed or interpreted seismic reflection data would instantly recognize the implications of the vastly different sampling rates on the resolution differential between the two cores.

  30. While the analysis is very intersting, I have my doubts about the shape of the above results. That is, if this is supposed to be a physical process of diffusion (some form of time-averaging of the CO2 signal).

    For some type of averaging process, I’d expect the more heavily averaged signal (blue on the LHS of the above chart) to lie somewhere inside the range of the red ponts.

    Instead, the points on the most extreme LHS are below the range on the RHS. And for that to happen, I assume there would need to be a process which removes CO2 from the ice (e.g. by chemical reaction).

    The least we could then say would be that the term “diffusion” is confusing.

  31. LazyTeenager says:
    January 2, 2011 at 2:52 am

    This is not explained very well.

    Is David proposing that CO2 is being removed from the snow by diffusion but N2 and O2 do not diffuse out of the snow thereby altering the ratio?

    I am going to make a wild guess that the relative diffusion rates of gasses in ice are known. So what are they. My intuition says that CO2 would be slower as the molecule is bigger and this is the opposite if what is leopard.

    The CO2 is not removed from the snow. It diffuses throughout a depth interval in the snow as it accumulates and is eventually compacted into firn and then ice. This process is a well established fact.

    Van Hoof et al., 2005 demonstrated that the diffusion process acts like a low pass filter on the CO2 “signal.”

    I am using the sample rates in two Holocene-aged cores to demonstrate a strong correlation between CO2 mixing ratio and sample rate – A relationship that should exist if the diffusion process is behaving like a low pass filter on the CO2 “signal.”

    There are no “N2” or “O2” data sets in the NOAA paleoclimatology library for either of these coring sites. The only results for a search of the “N” or “O2” variables were for cores in Greenland and Bolivia – There is no search option for “N2.” And only one data set actually included mixing ratios of N2 and O2 – GRIP Basal Ice Gas Concentrations.

  32. Nice comments.

    Of course, diffusion is both ways. What is important to realize is that equilibrium seeks the level outside. It has been less than 400 ppm for the last hundred years, so anything higher is seeking that low level, even though it was 20 times higher (according to stomata and other proxies) in the past.

    Forget about the other gases: Fick’s Law is independent of other gases, only the CO2 matters. David: Fick’s Law is a law. Molecules do not accumulate; on the contrary they become more diluted, if the concentration along the diffusion path is lower.

    My only take home message is that CO2 diffuses through ice. It is not trapped. There is no CO2 bubble “time machine”. We could argue all day about how much or how fast. Ice is even more complicated under pressure—it is heterogeneous, comprising faults and strata. It becomes compressed into polymerized structural features in a zig-zag pattern. The Scripps work proves that CO2 diffuses through normal ice, so that no method can measure what the initial amount was. There experiment just governed diffusion, not degassing. If the initial amount were higher than today, it will be measured closer to today’s ambient. If initial amount was lower (although we are at a CO2 starved state right now, plants would all die if we got much lower than 200 ppm, so if it were much lower in the past, we would not be here), then diffusion would be outside in.

    And yes, an increase in O2 [ ] from photosynthesis being amplified 20-fold would result, especially at ground level where the increase would be much higher. This increment could positively affect animals metabolism, depending on the local amount.

  33. bubbagyro says
    ————
    This is intuitively obvious to me, since the extreme size of dinosaurs 100 Mya required high CO2, parts per thousand, for plants to grow to supply them with food,; said plants could then generate the high oxygen levels the dinosaurs needed to maintain their metabolism at such high levels
    ————
    There would never be enough CO2 in the air to allow photosynthesis to [elevate] O2 by a significant amount.

    ==============================================

    Yet, the amount of O2 in atmposphere during the early carboniferous period was supposed to be over 30%

    http://en.wikipedia.org/wiki/Carboniferous

  34. Should be “Their” experiment in my comment.

    It is interesting to consider that a one millimeter diameter “bubble” in ice, if CO2 concentration were, say, one part per thousand (one thousand ppm), contains about a million billion molecules of CO2 (that is, a quadrillion)! Fick’s Law is statistical, and that many molecules racing around inside the bubble feverishly trying to get out should be conceptualized to appreciate how this works. At 250 degrees above absolute zero in ice, they are moving like crazy.

    Yes, diffusion is related to mass. CO2 has about 50% more mass than oxygen or nitrogen, so if diffusion coefficients are equal for CO2 and (O2 or N2) [they are not], then diffusion for O2 or N2 will be 50% faster based only on mass. That is irrelevant, because they act independently of CO2 and each other, and the concentration outside for N2 and O2 is the same inside, so there is no net flux for either N2 or O2 for the wee bubble.

  35. Diffusion occurs of course, but the question is how much? Consider the CO2 spikes during interglacials in the ice-cores. Wouldn’t those spikes have been gradually smoothed out farther down the ice-core, or at least show some indication of smoothing from significant diffusion? Graphs show distinct and sharp CO2 spikes during the interglacials all the way back at last 800k yrs.

  36. Michael says

    “The markets will front run the collapse. They seem to be starting to do that already. Buy Silver and Gold.”

    Sound advice. Note, however, that it is the metal which is necessary. When markets collapse, paper claims to metal will collapse along with all else. Owning real metal is a cumbersome practice, unfortunately.

  37. Dear Dave Middleton

    The sample rates were calculated by simply dividing the sample depth interval by the ice age interval:

    sr = [(zn – zn+1) / (tn – tn+1)]

    Where sr = sample rate (m/yr), z = sample depth (m) and t = ice age (yr)

    Your formula take no account of the static compression of the overlying ice. It is therefore invalid.

  38. Don’t forget that the density of the snow/firn/ice increases as you go down, so freshly trapped bolus of CO2 will find it easier to diffuse sideways and up. In those directions most of the diffusion is through the gas phase, while downwards, diffusion is increasingly through the liquid and solid phases. Thus, even if the gradient of CO2 concentration is steeper going down, the rate of diffusion in that direction will be reduced compared to what it would have been if snow density was constant in all directions.

  39. beng says:
    January 2, 2011 at 9:30 am

    Right on.
    Key concluding sentence from the paper by Scripps again*:
    The good fit of the model to the data supports our proposition that the CO2 originally trapped in the melt layer has diffused through the ice for thousands of years.

    *Journal of Glaciology, Vol. 54, No. 187, 2008
    CO2 diffusion in polar ice: observations from naturally formed CO2 spikes in the Siple Dome (Antarctica) ice core
    Jinho AHN,1,2 Melissa HEADLY,1 Martin WAHLEN,1 Edward J. BROOK,2 Paul A. MAYEWSKI,3 Kendrick C. TAYLOR4
    1Scripps Institution of Oceanography, University of California–San Diego, La Jolla, California 92093-0225, USA E-mail: jinhoahn@gmail.com 2Department of Geosciences, Oregon State University, Corvallis, Oregon 97331-5506, USA 3Climate Change Institute, University of Maine, 303 Bryand Global Sciences Center, Orono, Maine 04469-5790, USA 4Desert Research Institute, University of Nevada, 2215 Raggio Parkway, Reno, Nevada 89512-1095, USA

    And JT:
    We don’t have enough of a handle on the variables to say “how much”, just simply that diffusion of CO2 happens.

  40. Ah, Dave…I just looked at the Law Dome data ( ftp://ftp.ncdc.noaa.gov/pub/data/paleo/icecore/antarctica/law/law_co2.txt ) and I notice a little bit of a pattern in time…like the only data above 300 ppm is that dated after 1900 and, in fact, the data is not a scattering of points centered around a higher value…It is simply the march of CO2 levels upward in the last 100 years or so. The plot that you made completely obscures the very strong, steady dependence of the CO2 level on the mean air age in the Law Dome data! Since the Taylor core has such a low accumulation rate, it doesn’t have any data points in the post-industrial era!

    All that you have shown here is that if you don’t have enough data points to have ANY in the industrial era then you don’t see the post-industrial rise and if you do have any in the industrial era then you see the industrial rise.

  41. bubbagyro says:

    Yes. The experiment, CO2 diffusion in ice, has been performed at Scripps in 2008, demonstrating unequivocally that CO2 does indeed diffuse through ice at a rate that would be significant over years or decades timeframe, much less millenia or megayears, and initial concentrations will decrease if they are higher than the current ambient concentrations:

    “CO2 diffusion in polar ice : observations from naturally formed CO2 spikes in the Siple Dome (Antarctica) ice core
    Auteur(s) / Author(s)
    AHN Jinho (1 2) ; HEADLY Melissa (1) ; WAHLEN Martin (1) ; BROOK Edward J. (2) ; MAYEWSKI Paul A. (3) ; TAYLOR Kendrick C. (4)

    Journal of Glaciology ISSN 0022-1430 CODEN JOGLAO
    Source / Source
    2008, vol. 54, no187, pp. 685-695 [11 page(s) (article)] (1 p.1/2)”

    Here’s a copy of that paper, so that we are all on the same page: http://ns.geocraft.com/WVFossils/Reference_Docs/CO2_diffusion_in_polar_ice_2008.pdf Reading that paper does not seem to lead to the conclusions you draw. In particular, they note:

    (1) “Smoothing of the CO2 record by diffusion is one to two orders of magnitude smaller than the smoothing by diffusion in the firn at the depth of 287m (gas age = 2.74 kyr BP) in the Siple Dome ice, and so does not degrade the record.”

    (2) At depths where the ice age is tens of thousands of years (they use 80,000 years as an example), the diffusion may be comparable to the diffusion in firn and hence it may have “an impact on the smoothing of CO2 records on a decadal scale”. However, they admit that “there are no decadal CO2 data for
    ice that is 80 kyr old”. Hence, it would seem that their conclusion about smoothing is, at least at the moment, basically academic.

    (3) They also note factors that make the diffusion less of an issue for other ice cores: “Ice cores from colder sites than Siple Dome would experience slower CO2 diffusion in deep ice. The formation of clathrate ice (bubble-free ice) at depths from 500 to 1200m (25–65 kyr) at other Antarctic cold-drilling sites (Vostok, Dome Fuji and EPICA Dome C) is expected to result in highly reduced gas diffusion (Salamatin and others, 1998).”

    Perhaps your misreading of the paper stems from the fact that you are reversing how the timescales work. You seem to think their talk about what happens on years to decades mean much more diffusion will happen over longer times. However, what they are doing is looking at 80,000 year old ice and saying, “The amount of diffusion in this ice might be enough for the CO2 to migrate enough to smooth out the CO2 data over a time period of years to a decade or so.” Do you understand the difference?

    We don’t have enough of a handle on the variables to say “how much”, just simply that diffusion of CO2 happens.

    Not really. That paper concludes that it is at worst of marginal significance (i.e., it might in the worst case cause a comparable smoothing as the other known effects) and at best of no significance.

  42. John A says:

    January 2, 2011 at 9:46 am

    Dear Dave Middleton

    […]

    Your formula take no account of the static compression of the overlying ice. It is therefore invalid.

    The equation calculates a sample rate, not the accumulation rate.

    From the text of the post:

    Compaction effects due to burial can also add to the diffusion process.

    I can’t differentiate how much of the diffusion is due to accumulation rate and how much is due to compaction.

    For this particular exercise, I chose two relatively shallow cores. The compaction effects should be about the same in both cores.

    From one of my previous comments:

    The sample rate is a proxy for snow/ice accumulation rate and compaction. These are both rather shallow cores (Talyor Dome 357 m, Law Dome 535 m). So the compaction effects should be very minor relative to the accumulation rates and would likely be very similar in the two cores. The vastly different accumulation rates would dominate the sample rate calculation as it pertains to resolution.

  43. Can the equation then be used in reverse to estimate what the co2 levels would have actually been once mixing etc… are accounted for? Would be very interesting to see the results, even if only indicative!

  44. bubbagyro says
    ———–
    What this means is that 600 ppm in a bubble in ice with 300 ppm outside will deplete CO2 in the bubble until the outside concentration approaching 300 ppm is asymptotically reached. A concentration of 1200 ppm will diffuse twice as fast as 600, 2400 ppm 4 times as fast, etc. Twice the age, conversely, will have twice the time for diffusion, so old cores will be nearer outside equilibrium level
    ————-
    So are you saying that CO2 in deep ice is in equilibrium with the atmosphere?

  45. David Middleton says
    ———–

    The CO2 is not removed from the snow. It diffuses throughout a depth interval in the snow as it accumulates and is eventually compacted into firn and then ice. This process is a well established fact.
    ———-
    I don’t doubt the diffusion thing. What I am trying to figure out is your suggestion that the low-pass filter effect is reducing the measured concentration of CO2.

    The low-pass filter would reduce both up and down extremes of CO2 concentration and force the extreme values towards a time average of the concentration. The averaging would not bias the concentration to higher values which appears to be what you are suggesting.

    So I am guessing that I am not understanding some aspect if you explanation.

  46. Wow, nearly missed this posting, as it was released while the previous discussion of ice cores still is in it’s final state…

    To begin with: sample rate indeed has something to do with accumulation, but as the technique of sample analyses evolves, smaller and smaller samples are needed. Thus the relation is not 1:1, but sampling frequency increases for the more recent ice cores. That makes that:

    This makes it very clear that the low CO2 values in the Antarctic ice cores during the Holocene could easily be the result of diffusion and do not constitute valid evidence of a stable pre-industrial atmospheric CO2 level of ~275 ppmv.

    Is a little premature, as the correlation between sample rate and/or accumulation rate with CO2 levels is mostly spurious (as good as the ice age – gas age “correction” by J.J. Drake is based on a completely spurious correlation).

    What happens in the ice core with CO2 during the firn densification was measured in the Law Dome ice cores by Etheridge e.a.:

    http://www.agu.org/pubs/crossref/1996/95JD03410.shtml
    unfortunately behind a paywall.

    Migration of all molecules takes place in all directions, faster in the upper part of the firn, slower with depth, as the pores become smaller. That makes that:
    1. the heavier isotopes and heavier molecules are enriched (1-2%) by graviation with depth. That is corrected for, based on the measured 15N/14N enriching.
    2. the gas composition at bubble closing depth is a mix of several years. This averaging depends of the diffusion speed and the years necessary to reach the depth where vertical diffusion stops (mostly slightly above closing depth, due to more dense winter layers).

    Below the vertical diffusion stop depth, the compositions doesn’t change anymore and air samples in situ taken from the still open pores at bubble closing depth and from the bubbles in the ice cores (via the normal route of relaxation and transport, crushing under vacuum over a cold trap) have the same CO2 level.

    In the case of the Law Dome ice cores, the composition of the air at closing depth was only 10 ppmv CO2 below the CO2 level of the atmosphere. As that happened in the period that direct measurements were already done for decades at the South Pole, one could determine that the average age of the air was about 7 years older than at the surface (with a theoretical averaging based on diffusion speed of about a decade). That makes that the top meters of the ice cores and the direct measurements have an overlap of about 20 years. See the overview here:

    As one can see, the ice cores CO2 simply follows the atmospheric CO2 levels, be it smoothed over several years and is somewhat older (until much older), depending of the accumulation rate.

    About diffusion during densification in the firn:
    As already said by others, diffusion happens always from the highest level to the lowest level (in fact both ways, but faster from the highest level than reverse), as long as the pores are wide enough. Thus it is impossible to find 290 ppmv in the ice cores, if the atmosphere was higher than that for a period longer than the gas age averaging. Thus if one measures 290 ppmv in an ice core, either that was the average of a quite stable period with 290 ppmv in the atmosphere or it is the average of (large) swings over and below 290 ppmv. Thus any proxy that shows higher or lower levels over a period long enough to be detected in the ice core(s) averaging is biased. That includes historical measurements over land and stomata data…

    The (theoretical) smoothing of a peak of CO2, if that happens in a short period, can be seen here for the Law Dome ice core, together with a lot of other interesting items:
    http://courses.washington.edu/proxies/GHG.pdf

  47. where does the snow that falls on the ice pack come from ? Rain drops, snap frozen, from near zero will have huge amounts of CO2 inside:-

    http://www.engineeringtoolbox.com/gases-solubility-water-d_1148.html

    These data sets are very interesting in thinking about Keeling Ar/N2 ratios. Argon is completely inert and N2, though part of the biotic cycle, is in huge excess.
    From the slope of the Ar and N2 solubility curves one can see that the atmospheric ratio of Ar/N2 should change in a way which would give us a real temperature readings. If ocean temperatures were to rise from 0 to 20 degrees the solubility of N2 in water drops to 67% initial , whereas the solubility of Ar would drop to 56% initial. So the ration of Ar/N2 should give you the average temperature of the oceans between 0 and 20 degrees.
    This is why I asked about Ar and N2 in ice core data.

  48. As Tim Folkerts already said, the diffusion (theoretically) calculated from migration in the Siple ice core is very small. Here a comment on the same point I have made on the other ice core discussion:

    The migration of CO2 in ice cores was theoretically calculated by looking at the migration in remelted layers of a “warm” (-24°C) ice core, Siple Dome:
    http://catalogue.nla.gov.au/Record/3773250
    The extra smoothing of the gas age averaging caused by migration is about 2 orders of magnitude less than the averaging itself. For the Siple Dome ice core, the average gas resolution is about 22 years. Migration increases that with about 0.2 years.
    At lowest depth, the layers become thinner and migration may relatively increase and give a doubling of the resolution to some 40 years.

    The Vostok and Dome C ice cores are much older at depth, but also much colder (-40°C), which means less water (no water layer at all at -32°C, as long as no salt inclusions are involved). But there is a simple proof that migration doesn’t play a role at Vostok and Dome C:
    The Vostok (and Dome C) ice cores show a quite nice relationship between the temperature proxy (dD and d18O) and CO2 levels, be it with a lag. Nevertheless, the ratio between CO2 and temperature is about 8 ppmv/°C between interglacials and glacial periods over the past 420,000 years (recently confirmed for the full 800,000 years in Dome C). If there was some migration, the ratio would fade over time for each 100,000 years period further back. That is not the case. Thus there is little migration of CO2 in the Vostok and Dome C ice cores…

  49. I’ve wondered how accurate those ice core Co2 levels really are…..
    ====================================================
    Microbes can survive ‘deep freeze’ for 100,000 years

    Microbes can survive trapped inside ice crystals, under 3 kilometers of snow, for more than 100,000 years, a new study suggests. The study bolsters the case that life may exist on distant, icy worlds in our own solar system

    They say a tiny film of liquid water forms spontaneously around the microbe. Oxygen, hydrogen, methane and many other gases will then diffuse to this film from air bubbles nearby, providing the microbe with sufficient food to survive

    http://www.newscientist.com/article/dn12752-microbes-can-survive-deep-freeze-for-100000-years.html

  50. fhsiv says:
    January 1, 2011 at 6:46 pm

    Is the pattern of CO2 concentration versus depth/age the same in other ice cores? Does the CO2 level out at the same concentration? Is this what the warmers are relying on as evidence of a lower and stable pre-industrial CO2 concentration?

    There are huge differences with depth, simply because there are huge differences in accumulation rate. Despite that, it is possible to calculate (and measure for the high accumulation ice cores) the average age of the air at closing depth. Gas composition from extreme different ice cores (temperature, salt/dust inclusions) is the same (within 5 ppmv) for the same gas age in overlapping periods. Here for the past 1,000 years:

    Other processes play little role in Antarctica (more in Greenland ice cores): some bacteria use CO2 for DNA repair to survive the Vostok temperatures (0.1 ppmv!), clathrate formation plays a role, but clathrates are effectively destroyed under vacuum (at measurement time)…

  51. bubbagyro says:
    January 1, 2011 at 6:56 pm

    Practically, then, no old ice core can give an accurate result for ancient conditions using the traditional CO2 bubble gas chromatography method, and the result will be worse the higher the initial concentration of CO2 that existed in the past, and even worse the longer the residence time in the core.

    Only for the “warmest” ice cores, migration of CO2 in the core may play a minor role. Not detectable in the cold inland ice cores like Vostok or Dome C. The problem is reverse of what you wrote: we measure 180-300 ppmv in the ice cores, while the current atmosphere is at 390 ppmv. Thus if there was some migration, then the original levels at closing time would have been (much) lower than what is measured now, or there was very little migration…

  52. latitude says:
    January 2, 2011 at 2:56 pm

    I’ve wondered how accurate those ice core Co2 levels really are…..
    ====================================================
    Microbes can survive ‘deep freeze’ for 100,000 years

    They can “survive” but that is pretty all they can. In the Vostok ice core they use CO2 for DNA repair. The total amount used, when calculated from the total N2O level, is about 0.1 ppmv CO2. See:
    http://www.pnas.org/content/101/13/4631.full.pdf+html item K.

  53. Ferdinand Engelbeen says:
    January 2, 2011 at 4:27 pm
    They can “survive” but that is pretty all they can.
    ========================================================
    Oxygen, hydrogen, methane and many other gases will then diffuse to this film from air bubbles nearby, providing the microbe with sufficient food to survive
    =========================================================
    And diffuse from the next air bubble over, and diffuse from the next air bubble over from that one………..and on and on

    and over the course of a few thousand years…………….You’re diffused out

  54. As Beng says above (JAN 2 9:30AM) the peaks and troughs in the ice core record corresponding to the interglacials and glacials have about the same values over an approximately 800,000 year period.

    Why?

    If significant diffusion were persisting over the whole of that period, those peaks would all be diminishing over time.

  55. jimmi says:
    January 2, 2011 at 5:46 pm
    If significant diffusion were persisting over the whole of that period, those peaks would all be diminishing over time.
    =========================================================
    jimmi, I’m just adding a biological component.
    Which could also explain the elevated methane levels in ice cores.

    Oxygen moves about a lot easier in ice. In low oxygen conditions those microbes would be using CO2 and converting it into methane.

    Saying they would survive and that’s about all, is not true. They would slow down, but they are still performing functions. Something they might do in a day at normal temperatures, might take a decade or a hundred years or a thousand years, but it will still happen.

    There are elevated levels of methane in ice cores that have not been explained. Microbes converting CO2 to methane could explain that.

    That would reduce CO2 levels at lot more than is accounted for, and explain the elevated levels of methane which have not been explained all at the same time.

  56. Michael says: January 1, 2011 at 8:38 pm
    OT . . . Something that has always puzzled me about the US Civil War. It seems to
    [o] highly organized to have not been staged? We fell for the Civil War. Everything the Civil War accomplished could have been accomplished by legislation. Every other country in the world did it that way.

    As conspiracy theories go, that’s a doozy. ;-)
    Ever notice that the alleged Civil War coincides with the end of the Little Ice Age? Mere coincidence?

    Geoff Sherrington says: January 1, 2011 at 9:07 pm
    . . . If the Vostok hole, estimated older than 700,000 years, is deepened until there is no longer ice (but a lake or rock) – then what was the climate like 700,000 years ago before the ice was put in place? Some say the older ice was squeezed sideways into the oceans, but I think they are having a guess. . . .

    It was probably granitized.

    On topic, I’ve been wondering about CO2 diffusion through ice for a while, so the Scripps study will help, if I can find it.

  57. Given that we know weather and therefore climate is a dynamic process and that dynamic processes tend to have relatively high frequency signals of what ever it is we are measuring. I am the least bit surprised. I am also less then impressed with the ideas surrounding these space limited samples such as ice cores or tree rings. I am not convinced they represent what many seem to think they do. Finer the measurements the less reliable the representativeness of large districts or areas, let along the entire planet.

  58. latitude says:
    January 2, 2011 at 4:45 pm

    and over the course of a few thousand years…………….You’re diffused out

    If there is little difference between the levels, there is no driving force to diffuse out to another. If the microbes use or produce anything, there is a driving forse, but the diffusion rate decreases with the square of the distance and the reciproke of temperature. We are talking about microns between bacterial encapsulating and air bubbles, not meters of ice…

    latitude says:
    January 2, 2011 at 6:37 pm

    Saying they would survive and that’s about all, is not true. They would slow down, but they are still performing functions. Something they might do in a day at normal temperatures, might take a decade or a hundred years or a thousand years, but it will still happen.

    Please read the reference of bacterial functions in ice I gave you: the conditions in the Vostok ice core are such that the bacteria’s only remaining function is DNA/cell repair at an extremely low rate, all other functions are so slow as undetectable.

    From that source:
    Nitrifying bacteria with metabolic rate 10^-12 per hour at -40°C (point L) have been encased in liquid veins in Vostok ice for ~140,000 yr. At a rate of 10^-12 per hour, it takes 10^8 yr to turn over the carbon in their cells without growth.

    That is 100 million years to replace all carbon. One million years to replace 1/100th of the carbon content of the bacteria to survive. I have no idea of the total carbon content of all the microbes encapsulated in the Vostok ice cores, but I suppose that that it is far less than the CO2 content…

    Methane and other gases only have a significant migration rate (relevant for past air composition) at the lowest few hundred meters of the Vostok ice core (as well as in other ice cores – Greenland), where the temperature is increased due to earth warmth. That part of the core is not used for air measurements, also because the layers are disturbed. Mid-latitude glacier ice cores with higher average temperatures show relevant biolife and Greenland ice cores are unsuitable for CO2 levels, due to frequent (acid) volcanic dust inclusions from nearby Iceland.

  59. Geoff says:
    January 3, 2011 at 12:40 am

    One more time:
    van Hoof references:

    From the first link:
    The magnitude of the observed CO2 variability implies that inferred changes in CO2 radiative forcing are of a similar magnitude as variations ascribed to other forcing mechanisms (e.g. solar forcing and volcanism), therefore challenging the IPCC concept of CO2 as an insignificant preindustrial climate forcing factor.

    As said before in the other ice core/stomata discussion, stomata data are based on CO2 levels as being available over land (during the previous growing season). These are far more variable than and (positively) biased compared to “background” CO2 levels measured in 95% of the atmosphere (including smoothed in ice cores). Even if the bias over the past century can be removed by calibrating against ice cores, that is no guarantee that the same bias was at work in ancient times (changes in land use, climate related vegetation changes, climate related changes in main wind direction,…).

    Further, a local increase in the first 1,000 meters to 1,000 ppmv CO2 over land has hardly an influence on IR retainment and thus temperature: less than 0.1°C. Thus the influence of +34 ppmv near ground has no detectable influence at all.

    The remaining question is in how far the local measured CO2 levels over land via stomata data can be used as reference for global CO2 levels…

  60. Ferdinand at Jan 3rd, 12.40 am
    Ferdinand thank you for your short reply. You point us to van Hoof who writes in part-

    “The magnitude of the observed CO2 variability implies that inferred changes in CO2 radiative forcing are of a similar magnitude as variations ascribed to other forcing
    mechanisms (e.g. solar forcing and volcanism), therefore challenging the IPCC concept of CO2 as an insignificant preindustrial climate forcing factor.”

    Ferdinand, what is causing what? I can see no logical closed loop explanation of the quote above. English is my first language, but we must speak physics also. For example, some argue that TSI has hardly varied (Leif) and others note that the gas and particle composition from one volcano to another is not constant, thus allowing more unknowns in reconstructions.

    Can you please explain why you pointed to this? What is the relevance of hypothesising that some forcings equalled others?

    Also, still unanswered, what was the climate like at the time corresponding to the deepest ice in Vostok? Or anywhere else that has been measured deep in the Antarctic?

    For Greenland, there are papers speculating that ice core isotopes reflect, in part, the direction of winds bringing snow to the accumulation point. How is this effect accounted for at the South Pole? Ref: Steffensen, J. P., K. K. Andersen, et al. (2008). High-Resolution Greenland Ice Core Data Show Abrupt Climate Change Happens in Few Years. Science 321 (5889): 680–684.

    Still unanswered, does deep ice from near the South Pole indeed contain fragments of prior ice blown by wind, or does the whole reconstruction depend on the assumption of “pure as wind-blown snow?” Most of the oceans around the South Pole are more than 2,000 km distant.

    Still unanswered for J.J. Drake, how does one assume a conventional correlation of time with isotopes when the gas/ice age difference can be from 2,000 to 6,500 years?

    Re your van Hoof reference, can you point me please to a calibration with instrumentation (such as thermometry) and stomata properties? I note in partial reply that “plots of needle stomatal frequency as a function of atmospheric CO2 concentration constructed for four native North American conifer species – Tsuga heterophylla, Picea mariana, Picea glauca and Larix laricina – based on stomatal frequency measurements made on needles collected from living trees, herbarium samples and well-dated peat cores that could be assigned atmospheric CO2 concentrations corresponding to the times of the needles’ creation on the basis of historical atmospheric CO2 measurements and CO2 measurements of air bubbles trapped in shallow Antarctic ice cores”. (Kouwenberg, L.L.R., McElwain, J.C., Kurschner, W.M., Wagner, F., Beerling, D.J., Mayle, F.E. and Visscher, H. 2003. Stomatal frequency adjustment of four conifer species to historical changes in atmospheric CO2. American Journal of Botany 90: 610-619. )

    So, we have some circular argument from where you point us. Using ice bubbles to calibrate stomata to calibrate ice bubbles?

    Do you not think that stomata properties are afflicted by the same complexities as tree rings? For example, there is that troubling paper by Helliker, B. R. & Richter, S. L. Nature 454, 511–514 (2008), maintaining that leaves strive to a constant internal temperature – so what really does affect stomata properties?

    There is more unstated complexity. Kouwenberg et al. (above) concentrated their efforts on conifers, restricting their study to the range of atmospheric CO2 concentrations thought to be experienced over the past century. This was because most studies of stomatal frequency response to atmospheric CO2 enrichment had been conducted on the leaves of woody angiosperm taxa (Woodward, 1987; Peñuelas and Matamala, 1990; Paoletti and Gellini, 1993, Kurschner et al., 1996; Wagner et al., 1996; Wagner, 1998); and they have revealed, in the words of the authors, that “the maximum effect of the current CO2 increase on stomatal frequency has already been reached.”

    When you point us to van Hoof, do you understand these complexities? They could well be severe enough to invalidate the whole concept.

  61. Joel Shore says:
    January 2, 2011 at 10:57 am (Edit)
    Ah, Dave…I just looked at the Law Dome data ( ftp://ftp.ncdc.noaa.gov/pub/data/paleo/icecore/antarctica/law/law_co2.txt ) and I notice a little bit of a pattern in time…like the only data above 300 ppm is that dated after 1900 and, in fact, the data is not a scattering of points centered around a higher value…It is simply the march of CO2 levels upward in the last 100 years or so. The plot that you made completely obscures the very strong, steady dependence of the CO2 level on the mean air age in the Law Dome data! Since the Taylor core has such a low accumulation rate, it doesn’t have any data points in the post-industrial era!

    All that you have shown here is that if you don’t have enough data points to have ANY in the industrial era then you don’t see the post-industrial rise and if you do have any in the industrial era then you see the industrial rise.

    Joel,

    That’s correct. If I plot the CO2 mixing ratio against the calculated air age, it does make it look like the CO2 level rising above 300 ppmv is an anomalous feature of the industrial era. I’m not trying to recreate things that have already been done.

    Wagner et al., 1999 and Kouwenberg et al., 2005 showed large century-scale fluctuations in atmospheric CO2 levels from the Early Holocene up through the pre-industrial era. Van Hoof et al. 2005 was able to reconcile a 13th century stomata chronology with the ice core data by applying a low-pass filter to the stomata data. I simply used the ice core data to demonstrate that there is a strong correlation between a resolution proxy (sample rate) and CO2 mixing ratio – A relationship that should exist if the stomata data are reflecting the higher frequency component of the CO2 “signal.”

    I just realized that I failed to cite a key paper in my previous post:

    Wagner, F., Dilcher, D.L., Visscher, H., 2005. Stomatal Frequency Response In Hardwood Swamp Vegetation From Florida During a 60-Year Continuous CO2 Increase. American Journal of Botany 92(4): 690–695. 2005.

    Wagner et al. showed that the stomatal response of several hardwoods in Florida from 1940-2000 were consistent with the instrumental CO2 record.

    Stomata data show higher and more variable CO2 levels that ice cores during the pre-industrial Holocene, a low-pass filter of the stomata data matches the ice core data, the sample rate – CO2 correlation in the ice core data fits the low-pass filter model and the stomata data tie into the instrumental record.

  62. Latitude says
    ————-
    and over the course of a few thousand years…………….You’re diffused out
    ————-
    I am inclined to throw down a challenge to those keen on this idea. Calculate it!!!!

    The math is quite simple, once the diffusion coefficient of CO2 in ice is known, it could be approximated numerically with a spreadsheet. For those with no faith in computer models it can be calculated analytically.

    Here is a baseline problem:
    1000m of solid ice laid down at 200ppmv CO2
    A step change in CO2 to 300ppmv
    How long would it take the CO2 at 100m depth to change to 290ppmv?

    Shouldn’t take long for people who claim they are smarter than climatologists to work this out.

    Should sort the people who talk the talk from the people who walk the walk.

  63. There are several things that do not seem justified in this analysis.

    1/ You seem to be of the impression that “diffusion” of CO2 in the ice can somehow account for its concentration being lower than it appears to be in order to suggest a higher historical level and thus less human emissions. Where do you think it could “diffuse” to ?

    All this can explain is the inability to capture the high frequency signal but that is nothing new and widely accepted.

    2/ Figure 1 has Vostok in the title. That seems to be completely erroneous since there does not appear to be any Vostok data show, just Law and Taylor.

    3/ You give no reason or justification for you idea of fitting an exponential to the two sets of data. Why not a straight line or a square law or a hyperbola ? It seems an arbitrary choice.

    4/ Why do you do your fit to an ensemble of the two datasets. You are implicitly assuming parallel physical processes at the two sites. This assumption is not explained or justified and in particular does not seem reasonable. Even an eyeball glance at the two sets of data does not suggest that they are two parts of the same thing. Try fitting an exponential to each data set in turn and they will be wildly different.

    This makes it very clear that the low CO2 values in the Antarctic ice cores during the Holocene could easily be the result of diffusion and do not constitute valid evidence of a stable pre-industrial atmospheric CO2 level of ~275 ppmv.

    All I can read in this data “correlation” is a general trend to increasing CO2 levels that vaguely matches the increasing density of the ice with depth. These are two totally unrelated physical effects with a vaguely similar trends. Neither of these trends is a discovery and any correlation is neither surprising nor useful.

    Sorry, but this examination makes nothing “very clear” apart from the prejudice you brought to the exercise.

    It appears beyond all else that you are doing what most of climate science seems to be doing of late: starting out with a preconceived idea of what is the truth and setting out to prove it. Your prejudice is the opposite but the method is essentially the same.

    The major difference is that you seem to be untrained and hence mistakes are excusable. Those with PhDs to wave about can not plead ignorance and are intentionally misleading the world.

  64. Ferdinand Engelbeen says:
    January 3, 2011 at 2:12 am
    Please read the reference of bacterial functions in ice I gave you: the conditions in the Vostok ice core are such that the bacteria’s only remaining function is DNA/cell repair at an extremely low rate, all other functions are so slow as undetectable.
    ===================================================
    Ferdinand, I know it’s hard to have a written conversation, but don’t confuse disagreeing with not reading….
    ….I did read it
    I don’t agree with it.
    DNA/cell repair is the primary function of all micro organisms. That is what they mostly do all the time.
    All that is saying it that their metabolism has been slowed down.

  65. atmospheric concentrations of the past are the only major values which have originated numerous hypotheses concerning the past of our Globe, based on a unique measure : ice cores. All the theories concerning very different scientific subjects have been routinely (and successfully) confirmed by different measures using totally different properties.
    So, it should be not at all surprising to discover one day or the other that this beautiful house of cards has suddenly collapsed due to new, simple observations.

  66. P. Solar says:
    January 3, 2011 at 5:10 am (Edit)
    There are several things that do not seem justified in this analysis.

    1/ You seem to be of the impression that “diffusion” of CO2 in the ice can somehow account for its concentration being lower than it appears to be in order to suggest a higher historical level and thus less human emissions. Where do you think it could “diffuse” to ?

    All this can explain is the inability to capture the high frequency signal but that is nothing new and widely accepted.

    Apply a low-pass filter to any high frequency data set and you will attenuate the amplitude range.
    HadCRUT3 Amplitude Attenuation Using a Low-Pass Filter

    2/ Figure 1 has Vostok in the title. That seems to be completely erroneous since there does not appear to be any Vostok data show, just Law and Taylor.

    Good catch. I am also working on taking this back to the Pleistocene with the Vostok core. I’ll fix the title of this particular image when I get a chance.

    3/ You give no reason or justification for you idea of fitting an exponential to the two sets of data. Why not a straight line or a square law or a hyperbola ? It seems an arbitrary choice.

    It was the best fit. A linear fit also yields a pretty decent R^2. I used a log scale on the x-axis to separate the two cores. A linear scale shows them overlapping.
    Ideally, I would like to find an Antarctic core with an accumulation rate that falls between Taylor and Law Domes.

    4/ Why do you do your fit to an ensemble of the two datasets. You are implicitly assuming parallel physical processes at the two sites. This assumption is not explained or justified and in particular does not seem reasonable. Even an eyeball glance at the two sets of data does not suggest that they are two parts of the same thing. Try fitting an exponential to each data set in turn and they will be wildly different.

    Because I am analyzing the correlation of sample rate to CO2 mixing ratio across different cores with different accumulation rates across different periods of time.

    This makes it very clear that the low CO2 values in the Antarctic ice cores during the Holocene could easily be the result of diffusion and do not constitute valid evidence of a stable pre-industrial atmospheric CO2 level of ~275 ppmv.

    All I can read in this data “correlation” is a general trend to increasing CO2 levels that vaguely matches the increasing density of the ice with depth. These are two totally unrelated physical effects with a vaguely similar trends. Neither of these trends is a discovery and any correlation is neither surprising nor useful.

    Sorry, but this examination makes nothing “very clear” apart from the prejudice you brought to the exercise.

    It appears beyond all else that you are doing what most of climate science seems to be doing of late: starting out with a preconceived idea of what is the truth and setting out to prove it. Your prejudice is the opposite but the method is essentially the same.

    The major difference is that you seem to be untrained and hence mistakes are excusable. Those with PhDs to wave about can not plead ignorance and are intentionally misleading the world.

    It is a relationship that should exist if the reconciliation of ice core and stomata in van Hoof et al., 2005 is valid.

  67. Geoff Sherrington says:
    January 3, 2011 at 2:55 am

    Ferdinand, what is causing what? I can see no logical closed loop explanation of the quote above. English is my first language, but we must speak physics also. For example, some argue that TSI has hardly varied (Leif) and others note that the gas and particle composition from one volcano to another is not constant, thus allowing more unknowns in reconstructions.

    Leif is right about the TSI, but TSI is not the only (or even main) influence of the sun (see the latest discussion about the changes in UV). And indeed one volcanic explosion is not another… Anyway, what Van Hoof suggests is that if there was a higher variability of CO2 in the past, then the influence of CO2 on temperature/climate was higher than expected. I doubt that: the variability of CO2 in the stomata data anyway is local/regional variability with (very) limited influence on climate. Only if the local variability really reflects a global variability, then it may be influencing climate to some extent.
    My impression is opposite: a small change in temperature causes a small global change in CO2 levels, but may induce a more important change in local/global CO2 levels over land, as both soil bacteria become more active and plants grow harder (if not beyond their optimum). The result is an increased positive bias, as the effect of night respiration on CO2 levels increases more than daylight photosynthesis, as during the day there is a better mixing with the overlying (background CO2 level) air. Many other factors may be involved too: During the LIA, the Gulf Stream was far more South (Portugal, later North Africa) than during the MWP or current. With possible changes in main wind direction (and thus average CO2 levels over land)…

    Also, still unanswered, what was the climate like at the time corresponding to the deepest ice in Vostok? Or anywhere else that has been measured deep in the Antarctic?

    There are several indications of the climate of many millennia ago, mainly based on isotope changes:
    – dD (deuterium/hydrogen ratio) and d18O in the ice water molecules reflect the temperature of the oceans where the water evaporated and partly the temperature of the air where the vapour cooled down to water/snow. See Jouzel e.a.:
    http://parrenin.frederic.free.fr/PRO/publications/download/articles/jouzel-JGR2003.pdf
    For coastal ice cores, the precipitation comes mainly from the nearby Southern Ocean, while the high altitude inland cores reflect more the whole SH oceans temperatures.
    – d13C of CO2 in the gas phase reflects increasing/decreasing vegetation.
    – d18O from N2O in the gas phase is inversely correlated with ice sheet formation (I don’t remember why…)
    etc…

    For Greenland, there are papers speculating that ice core isotopes reflect, in part, the direction of winds bringing snow to the accumulation point. How is this effect accounted for at the South Pole?

    Which is important for Greenland, as there are both lots of land and oceans nearby, but less important for Antarctica, as the circumpolar vortex mixes it all from over the oceans…

    Still unanswered, does deep ice from near the South Pole indeed contain fragments of prior ice blown by wind, or does the whole reconstruction depend on the assumption of “pure as wind-blown snow?” Most of the oceans around the South Pole are more than 2,000 km distant.

    The few mm ice equivalent per year at the high altitude Antarctic cores indeed may have been mixed or blown away or piled up by winds over several years. Not very important, as the (gas) averaging at Vostok is about 600 years… The ice layers are not counted as yearly layers either. Ice samples were taken each meter, reflecting about 20 year intervals (I suppose that this reflects the average years of the sample too) at the top to over 600 years at lowest depth.

    Still unanswered for J.J. Drake, how does one assume a conventional correlation of time with isotopes when the gas/ice age difference can be from 2,000 to 6,500 years?

    gas age and ice age are independent of each other. There is a direct dependence of ice age at closing depth with the accumulation rate and the closing depth itself depends of temperature. The gas age at closing depth depends on migration speed, which depends on pore diameter (=ice density) and temperature. Thus while there are common factors at work (accumulation rate and temperature influences the period that the pores still are open enough to allow migration) there is no physical connection between ice age and gas age at all.

    The main problem is that ice age is easy to establish: directly via counting the layers or indirectly via different methods: conductivity, H2O2 levels,… But gas age isn’t easy. There are gas diffusion models, which are confirmed by direct measurements in shallow ice cores (Law Dome), but an additional problems is that during glacials there is far less precipitation, thus the gas age may get a lot younger, thus increasing the ice age – gas age difference.

    Anyway, even within this uncertainty, there is enough evidence that CO2 levels of the same age in the gas phase follow the temperature changes (from isotope changes in the ice phase), not reverse. And that there is a quite nice fixed ratio between CO2 levels and the temperature (proxy). The ice age – gas age difference plays no role at all (as long as the average dates for each phase are correct).

    This is getting quite long, more in next message…

  68. LazyTeenager says:
    January 3, 2011 at 4:45 am
    I am inclined to throw down a challenge to those keen on this idea. Calculate it!!!!
    ===========================================================
    That’s the problem Lazy, you can’t calculate it.

    Ice cores are full of microbes/bacteria that convert CO2 to methane.
    That will lower CO2 levels, and it explains the reason the methane levels are elevated way above atmospheric methane levels – at least 10 times above.

    When you look at the biological component of ice cores, it makes the whole science of trying to reconstruct CO2 levels from ice cores worthless.

  69. Fig 1 seems to just show that more chronologically compact (and therefore deeper and older) ice has less CO2 than less chronologically compact ice. Diffusion before the bubbles are sealed implies that the CO2 record will be smoothed considerably at a decadal or century time scale for most cores, or at a millenial time scale for Vostok, which has very slow accumulation. But it won’t change the average CO2, so the AGW argument that current CO2 (approaching 400 ppm) is substantially higher than the last several thousand years (on average) still stands.

    However, Dana Royer and co-authors (GSA Today, March 2004, pp. 4-10 and Geochimica vol. 70, 2006, pp. 5665-75) note that over most of the last 550 million (not thousand) years, CO2 has mostly been in the range 1000-3000 ppm, and that levels under 500 ppm like the last few million years and the late Carboniferious/early Permian period have generally ben periods of glaciation. They characterize under 1000 ppm as “cool”.

    This implies that life in general and in particular the oceans do just fine with 1000-3000 ppm. It’s hard to say what the causality is — does high CO2 cause warmth or does a warm climate cause high atmospheric CO2 as the oceans degas — but it’s worth considering whether 500-1000 ppm might protect us against the otherwise inevitable next ice age without excessive warming.

    Bubbagyro (1/1 @ 6:56 AM) makes the very interesting point that CO2 may diffuse through ice. This implies that ice absorbs some CO2, and this absorption must vary with temperature. Snow itself will have some CO2 as it falls, but on the ground it will tend to be at a higher temperature than it was when it formed. It may then either absorb or degas CO2 from/into the adjacent air bubbles over time. This could completely screw up the ice core CO2 record, if it is a big enough effect. (Bubbagyro cites Ahn et al, CO2 Diffusion in Polar Ice…, J. Glaciology 54 (2008): 685-95, which I haven’t looked at yet.)

    Even if the net absorption/outgassing is small, this diffusion will continue to smooth the CO2 record long after the firn bubbles are sealed, and hence will make the ice core CO2 record look excessively flat.

  70. “This implies that life in general and in particular the oceans do just fine with 1000-3000 ppm.”
    =====================================================
    Or that that’s the optimum level that almost everything evolved, corals, plants, etc.
    That’s almost the optimum level for plant growth, which is 1500-2000 in the lab.

    The bigger question is why or what has made CO2 levels so low and are we in danger of CO2 levels being too low.

    Obviously, the planet has more things growing on it that are using CO2. Considering that those things evolved when CO2 levels were a lot higher….

    ….we should be more worried about raising CO2 levels than lowering it

  71. Geoff Sherrington says:
    January 3, 2011 at 2:55 am

    More for Geoff:

    Re your van Hoof reference, can you point me please to a calibration with instrumentation (such as thermometry) and stomata properties?
    and
    So, we have some circular argument from where you point us. Using ice bubbles to calibrate stomata to calibrate ice bubbles?

    I have no direct references about the influence of temperature, drought, etc… on stomata index level. I suppose these have their influences. My objections against stomata data is that the CO2 levels of which they are based on are not background CO2 levels, more variable and positively biased with unknown changes in local/regional variability and bias over time.
    And as stomata are proxies, not direct data, they need to be calibrated: to direct atmospheric measurements when available, or ice cores if not. Not reverse: stomata data accuracy is quite rough (+/- 10 ppmv), compared to e.g. the Law Dome (10-year filtered data) accuracy of +/- 1.2 ppmv. And as you have referenced, they have a limited range: above and below that range, there is no effect anymore. Comparable to the limited response of tree rings to temperature changes…

    So, I am not defending the stomata data: they give a good high frequency first approximation, but the ice core data are far more reliable, because that are direct measurements of background CO2 levels, be it smoothed over longer time periods: from a decade to 600 years for the youngest to oldest cores.

  72. latitude says:
    January 3, 2011 at 6:38 am

    That’s the problem Lazy, you can’t calculate it.

    Ice cores are full of microbes/bacteria that convert CO2 to methane.
    That will lower CO2 levels, and it explains the reason the methane levels are elevated way above atmospheric methane levels – at least 10 times above.

    When you look at the biological component of ice cores, it makes the whole science of trying to reconstruct CO2 levels from ice cores worthless

    Latitude, you are confusing between mid-latitude (warm) ice cores and the (very) cold ice cores like most in Antarctica. The CH4 levels from the Vostok (and other) ice core(s) are available and show the same (even more spectacular) HS curve as CO2 and N2O: all since the start of the (agricultural and) industrial revolution. See:
    http://www.pnas.org/content/94/16/8343.full
    and
    http://zipcodezoo.com/Trends/Trends%20in%20Atmospheric%20Methane.asp

  73. Hu McCulloch says:
    January 3, 2011 at 6:51 am

    Nice to see you here (it is a bit calm at CA these days, I can imagine it that it takes a lot of one’s life to maintain a blog like this one or CA…).

    I do agree with most of what you said, but some comment on:

    Bubbagyro (1/1 @ 6:56 AM) makes the very interesting point that CO2 may diffuse through ice.
    and
    Even if the net absorption/outgassing is small, this diffusion will continue to smooth the CO2 record long after the firn bubbles are sealed, and hence will make the ice core CO2 record look excessively flat.

    The article shows that the total migration is lengthening the averaging of the CO2 levels by the “warm” Siple ice core from 22 years to 22.2 years at medium depth, up to a doubling (40 years) at deepest ice. The much colder Vostok ice core doesn’t show any flattening of the ratio between (gas phase) CO2 vs. the (ice phase) temperature proxies over each 100,000 interglacial/glacial transition. Thus there was no measurable CO2 migration.

  74. Ferdinand Engelbeen says:
    January 3, 2011 at 7:30 am
    Latitude, you are confusing between mid-latitude (warm) ice cores and the (very) cold ice cores like most in Antarctica.
    =========================================================
    No I’m not….
    “Microbes” have been found in all depths, in all ice cores.

    I know biology can get in the way of all these neat little formulas, and the tendency is to ignore it when you can’t explain it.
    But it doesn’t change the truth.

    Until someone can explain how many bacteria/microbes are present or even explain what they are doing, account for every temperature change and qualify their rate of metabolism at each temperature because ice does change temperature………….

    Biology throws a monkey wrench into ice core temperature reconstructions, and until biology is explained, those reconstructions are worthless.

  75. latitude says:
    January 3, 2011 at 7:12 am
    ….
    The bigger question is why or what has made CO2 levels so low and are we in danger of CO2 levels being too low.

    I’m thinking that in the absence of major vulcanism caused by colliding continental plates to replenish the CO2, the biosphere slowly slurps the CO2 up, converting it into fossil fuels and limestone. Eventually (as during the Carboniferous and Neogene), CO2 gets so low that the globe is vulnerable to ice ages. Perhaps restoring some of that fossil CO2 to the atmosphere (up to 500-1000 ppm) would prolong the Holocene indefinitely?

    Just a suggestion, but no crazier than CAGW…

  76. Hu McCulloch says:
    January 3, 2011 at 9:09 am
    Eventually (as during the Carboniferous and Neogene), CO2 gets so low that the globe is vulnerable to ice ages
    ===============================================
    Hu, I don’t think there’s any correlation between CO2 and ice ages other than CO2 follows temperature changes. Which makes perfect sense. When temps warm metabolisms speed up, when temps fall metabolisms slow down. We forget that bacteria/microbes rule this planet.

    I agree with you 100% on the CO2/carbon connection. The planet seems to need that carbon and is very good at using it.

    If you consider that everything jump started when CO2 levels were high, temperatures went all over the place anyway, and CO2 levels have been consistently falling ever since.

    The only real hockey stick is not Hansens, it’s the one that shows CO2 levels falling.

  77. “”””” Joel Shore says:
    January 1, 2011 at 7:48 pm
    Ah, Dave…I just looked at the Law Dome data “””””

    Joel, if there did exist such an out diffusion process; as has been postulated here, and evidently confirmed at Scripps, would not that lead to a situation where the very newest core samples would be expected to be most like the conditions at formation; and older samples would be expected to gradually fall further back from the formation conditions.

    So the signature for such an effect would be a rising CO2 (sample) record for the last century or even a couple of centuries.

    So your argument that the rising data in the cores since 1900 represents the rising atmospheric levels (which we know confidently from Mauna Loa only since 1957/8) , is not really any more robust than the model where the trapped gases simply out diffuse per Fick’s Law.

    As an aside; in the early days of “Sampling Oscilloscope” technology; that being basically the early 1960s for commercially available instruments, it was believed that the rise time of the “scope” was limited by the length of the sampling pulse; so designers (at Tektronix, and Hewlett Packard) spent time trying to make ever shorter sampling gate drive pulses; using Tunnel Diodes, and the like. These efforts were hindered by the ability to make stable very low capacitance sample storage capacitors, so only small amounts of charge were collected during the short sampling pulse; so the early instruments were quite noisy; the noise being of the order of the square root of the number of electrons collected. (Shot Noise )

    In the later 1960s it was discovered that in fact the rise time (inverse bandwidth) was not set by the width of the sampling pulse; but was instead determined by the time taken to switch the sampling gate off; in other words the fall time of the sampling gate drive signal. Short shutoff times were generally easier to achieve, than short pulse lengths.

    This is pertinent to the ice core record; as the same phenomenon is in effect. The time taken to capture the atmospheric gas sample is not particularly significant; but the gate shutoff time is; that is the period where the air bubbles and the snow sample is being compacted to a degree, where the sample can be said to be truly encapsulated. And that period is evidently decades to perhaps centuries.

    So of course fast spikes to higher CO2 levels are simply not going to be recorded, when it takes so long to close the barn door.

    I’m generally skeptical of the value of the absolute levels of CO2 or Oxygen in the ice cores. The O2 in the ice is of no interest, since nobody knows when that H2O molecule was formed; it could be billions of years old; so only the O2 in the atmospheric samples has any proxy value.

    But I’m not too concerned about the problem; because I don’t think CO2 is in much of a controlling position, as regards the global mean Temperature; compared to the negative feedback cooling effect due to clouds.

  78. George E Smith says:

    Joel, if there did exist such an out diffusion process; as has been postulated here, and evidently confirmed at Scripps, would not that lead to a situation where the very newest core samples would be expected to be most like the conditions at formation; and older samples would be expected to gradually fall further back from the formation conditions.

    First of all, what the Scripps paper shows is that diffusion occurs but the rate is such that under perhaps the most extreme conditions (ice core in a warm place and the oldest part of the core) it could almost be comparable to other smoothing effects and otherwise it is much smaller. Second, it is not an “out diffusion” process…It is simply diffusing from higher concentration to lower concentration. Why would this result in a lowering of the CO2 in the core?

    So the signature for such an effect would be a rising CO2 (sample) record for the last century or even a couple of centuries.

    So your argument that the rising data in the cores since 1900 represents the rising atmospheric levels (which we know confidently from Mauna Loa only since 1957/8) , is not really any more robust than the model where the trapped gases simply out diffuse per Fick’s Law.

    Again, I see no reason why the diffusion should work preferentially in one direction. What it would do, if it does anything on any length scale that matters, is smooth things. And, there is no evidence that it does that.

    The supposed evidence presented in this post falls apart completely once one realizes that one isn’t just comparing different sampling rates but different time periods; the higher concentrations for the Law Dome core are simply due to sampling after the Industrial Age buildup began. Remove that data and the effect disappears. This is a classic case of correlation not meaning causation. David M.’s plot basically drops a lot of relevant information (the dependence of the measured CO2 levels on the time period that the core is measuring) and so detects an entirely spurious correlation between CO2 levels and sampling rate that is really just due to the dependence of CO2 levels on time.

    It would be just as meaningful as if I took a pot of room temperature water and sat it out on the counter and measured its temperature every 10 minutes. Then, I put it on the stove and start measuring its temperature every minute. I plot the data like David has and say, “Look…The measured temperature seems to depend on the sampling rate because the temperature is higher on average when I measure every minute than when I measured every ten minutes!”

  79. latitude says:
    January 3, 2011 at 8:48 am

    No I’m not….
    “Microbes” have been found in all depths, in all ice cores.

    Indeed, but at some depths more than other and some cores more than others. From the link you have read:
    Sowers (10) reported peaks in the concentrations of N2O and d15N of N2O and dips in the values of d18O of N2O occurring at the same depths in Vostok ice where Abyzov et al. (1) found peaks in bacterial concentration and where Petit et al. (48) found peaks in dust concentration. The ice temperature at that depth is -40°C. The remarkable correlation strongly suggests that, during the penultimate glacial maximum 140,000 years ago, dust and microorganisms were windborne with greater than normal efficiency and deposited onto Antarctic ice.

    The effect of this peak in dust and bacteria is a deficit of 0.1 ppmv CO2 over 140,000 years. If we may assume that the number of bacteria is directly related to dust deposits in the ice core, then the effect over time for the deepest useable part at a glacial maximum in the core is not more than 0.3 ppmv. Hardly a reason to reject the data.

    The temperature data from the Vostok borehole should be here:
    http://www.nature.com/nature/journal/v381/n6584/abs/381684a0.html
    but I don’t want to pay the scandalous sum they ask for an over 10 years old article. An average of -40°C is often said, with the not used ultimate bottom layers above Lake Vostok at higher temperature.

    Further, Antarctic coastal ice cores at higher temperature and far more dust/bacteria/salt/algue inclusions show very similar CO2, CH4, N2O,… levels for the same gas age. Thus not much influence from the microbes…

  80. Ferdinand Engelbeen says:
    January 3, 2011 at 11:17 am
    Further, Antarctic coastal ice cores at higher temperature and far more dust/bacteria/salt/algue inclusions show very similar CO2, CH4, N2O,… levels for the same gas age. Thus not much influence from the microbes…

    Ferdinand, thats interesting, because dust was the reason given for the redrawing of the Greenland ice cores so that they matched the Antarctic ice cores…
    http://tallbloke.wordpress.com/2010/12/28/tom-van-hoof-historical-co2-records/

    Any idea why that might be?

  81. George E. Smith says:
    January 3, 2011 at 10:04 am

    Joel, if there did exist such an out diffusion process; as has been postulated here, and evidently confirmed at Scripps, would not that lead to a situation where the very newest core samples would be expected to be most like the conditions at formation; and older samples would be expected to gradually fall further back from the formation conditions.

    So the signature for such an effect would be a rising CO2 (sample) record for the last century or even a couple of centuries.

    Sorry George, but Joel is right: Fick’s Law and diffusion works only from high to low. The only possibility for the opposite flow is by reverse osmosis, which needs a lot of pressure difference (and the right porosity) which doesn’t exist between ice layers at 70 and 71 meter or 3000 and 3001 meter. Thus forget “out” diffusion. It doesn’t exist.
    Moreover, if there was out diffusion, that would work for every gas, even better for the smaller ones: methane, Ar, O2, N2… than for CO2. Thus enriching the CO2 levels.

    Further, I can only agree with Joel that the sampling rate and CO2 levels have nothing to do with each other: The oldest Siple Dome samples (Neftel, 1992) used two sampling methods: 3 samples, each covering 220 years (!) and a “newer” method, with 12 samples each covering 11-12 years. If you average the higher resolution samples, you will find the same CO2 levels for the same average gas age. See Neftel e.a.:
    http://www.biokurs.de/treibhaus/180CO2/neftel82-85.pdf

    Further the 3 youngest gas age samples overlap with the direct measurements in the atmosphere and all samples overlap with the Law Dome ice cores samplings, which have a sampling rate of 2-5 years in the overlapping years with similar CO2 levels…

    Thus George (and David) there is no Sample Rate Problem, only a problem of a spurious correlation…

  82. Ferdinand, you keep quoting that one paper like it’s the only game in town.
    It’s not.
    There’s a lot more out there that says bacteria are active in ice, that bacteria tend to be equally distributed in ice cores no matter where they are collected, etc

    You can not draw a correlation between wind blown dust and bacterial populations simply because bacteria can reproduce in ice. Bacterial populations will flux because of that. The only correlation that can be assumed is that bacteria are attracted to the layers of dust because they are using that as food.

    There is nothing else that can explain the high methane levels in ice cores.
    And the simplest explanation is usually the right one.

    Bacteria can live and grow in ice, bacteria will use CO2 and create methane.

  83. tallbloke says:
    January 3, 2011 at 11:48 am

    Ferdinand, thats interesting, because dust was the reason given for the redrawing of the Greenland ice cores so that they matched the Antarctic ice cores…
    http://tallbloke.wordpress.com/2010/12/28/tom-van-hoof-historical-co2-records/

    Any idea why that might be?

    The difference is in the type of dust: dust in Antarctica is mainly sea salt (composed of mostly NaCl but also carbonate and other salts), far more at coastal sites than at altitude far more inland. During glacials, there is far less water vapour/clouds/rain/snow and dust from far away (even sand) can easier reach the inland ice cores. The highest dust levels in the Vostok ice core are measured just before a new interglacial, when temperatures are at its lowest.
    In the Greenland ice cores we have the same points (but in general a one order higher amount of dust than in coastal Antarctic cores) + an additional source: frequent volcanic eruptions from Iceland volcanoes. Iceland is at a hot spot and volanic ash is from the deep earth crust, quite toxic and very acidic (HCl, HF). When that is deposited in the layers of the Greenland ice core, that reacts over time with the sea carbonates and produces extra CO2 in situ…
    Some references:
    http://cat.inist.fr/?aModele=afficheN&cpsidt=3634884
    http://europa.agu.org/?view=article&uri=/journals/jc/97JC00163.xml

  84. latitude says:
    January 3, 2011 at 12:35 pm

    Ferdinand, you keep quoting that one paper like it’s the only game in town.
    It’s not.

    That one paper is a very good overview of the existing knowledge about bacterial life in ice cores.

    There’s a lot more out there that says bacteria are active in ice, that bacteria tend to be equally distributed in ice cores no matter where they are collected, etc

    That is certainly not true for the Vostok ice core.

    You can not draw a correlation between wind blown dust and bacterial populations simply because bacteria can reproduce in ice. Bacterial populations will flux because of that. The only correlation that can be assumed is that bacteria are attracted to the layers of dust because they are using that as food.

    Which means that the population around dust is (far) higher than at other places.

    There is nothing else that can explain the high methane levels in ice cores.
    And the simplest explanation is usually the right one.

    I don’t know which ice core you mean: the methane levels in all Antarctic ice cores are very low: between 300 and 700 ppbv during glacials to interglacials. Since about 6,000 years ago that increased to 800 ppbv until about 1850. Since then the levels increased to currently 1900 ppbv in the atmosphere.

  85. “”””” Ferdinand Engelbeen says:
    January 3, 2011 at 11:56 am
    George E. Smith says:
    January 3, 2011 at 10:04 am

    Joel, if there did exist such an out diffusion process; as has been postulated here, and evidently confirmed at Scripps, would not that lead to a situation where the very newest core samples would be expected to be most like the conditions at formation; and older samples would be expected to gradually fall further back from the formation conditions.

    So the signature for such an effect would be a rising CO2 (sample) record for the last century or even a couple of centuries.

    Sorry George, but Joel is right: Fick’s Law and diffusion works only from high to low. The only possibility for the opposite flow is by reverse osmosis, which needs a lot of pressure difference (and the right porosity) which doesn’t exist between ice layers at 70 and 71 meter or 3000 and 3001 meter. Thus forget “out” diffusion. It doesn’t exist. “””””

    So you don’t like my usage of terms; so let me redefine; For OUT diffusion read IN diffusion; as in CO2 diffusing INTO THE ICE; which just co-incidently is diffusion OUT of the trapped air samples, INTO the cie walls around the air bubble; where rumor has it the CO2 abundance is much lower than in the air; hence the reason why Fick’s Law would be applicable; and my comment stands.

    NO I WAS NOT MEANING DIFFUSION OF CO2 FROM THE TRAPPED POCKETS OUT INTO THE AMBIENT ATMOSPHERE.

  86. “”””” Joel Shore says:
    January 3, 2011 at 10:45 am
    George E Smith says:

    Joel, if there did exist such an out diffusion process; as has been postulated here, and evidently confirmed at Scripps, would not that lead to a situation where the very newest core samples would be expected to be most like the conditions at formation; and older samples would be expected to gradually fall further back from the formation conditions.

    First of all, what the Scripps paper shows is that diffusion occurs but the rate is such that under perhaps the most extreme conditions (ice core in a warm place and the oldest part of the core) it could almost be comparable to other smoothing effects and otherwise it is much smaller. Second, it is not an “out diffusion” process…It is simply diffusing from higher concentration to lower concentration. Why would this result in a lowering of the CO2 in the core?

    So the signature for such an effect would be a rising CO2 (sample) record for the last century or even a couple of centuries.

    So your argument that the rising data in the cores since 1900 represents the rising atmospheric levels (which we know confidently from Mauna Loa only since 1957/8) , is not really any more robust than the model where the trapped gases simply out diffuse per Fick’s Law.

    Again, I see no reason why the diffusion should work preferentially in one direction. What it would do, if it does anything on any length scale that matters, is smooth things. And, there is no evidence that it does that. “””””

    Joel, see my response to Ferdinand. I’m quite prepared to accept that Fick’s Law deals with diffusion from a place of high concentration to a place of lower concentration. Have I told you of my past life of diffusing ZINC into GaAs0.6P0.4 in sealed ampoule. When using ZnAs2 as the zinc source, the diffusion is rapid and the doping level achieved is high.; but when a GaZn alloy source is used the diffusion is very slow, and much lower doping density is achieved in deeper layers. So I do understand Fick’s Law.

    And when trapped air samples are entombed in a coffin of ice; which compressed from snow; that ice is depleted of CO2 by the segregation coefficient for CO2 at the freezing interface between liquid water and solid ice.

    So the diffusion of CO2 OUT from the trapped CO2 containing air INTO the CO2 depleted Ice is driven by the concentration gradient from air into ice, and depends on the activation energy for whatever the ambient (ice) Temperature is.

    I did NOT say the CO2 diffuses OUT to the ambient air (which conceivably could be of higher CO2 abundance.)

    You have to read what I write; not what you think I wrote or meant. I write what I mean; except when I make a misteak.

  87. George E. Smith says:
    January 3, 2011 at 1:51 pm

    So you don’t like my usage of terms; so let me redefine; For OUT diffusion read IN diffusion; as in CO2 diffusing INTO THE ICE; which just co-incidently is diffusion OUT of the trapped air samples, INTO the cie walls around the air bubble; where rumor has it the CO2 abundance is much lower than in the air; hence the reason why Fick’s Law would be applicable; and my comment stands.

    Quite confusing, your use of IN and OUT, I must say…

    Well, let’s take it that way:
    – I don’t see any reason why the migration into the intercrystalline waterlike layer would start when all bubbles are closed, it would start at the very moment that the first snowflakes are sintering together (as far as it happens). Or if you really mean the ice itself, then already when the snowflakes were formed.
    – The ice is itself is not a matrix that allows CO2 to be included. CO2 in many cases is measured in dry air by trapping water vapor over a cold trap: no measurable amount of CO2 is trapped in the matrix (we are not talking here about nanograms of dope!).
    – three methods were/are used to measure CO2 from ice cores: the old method was by melting all ice and applying vacuum to remove CO2 from the water phase. That did show a deficit of a few ppmv compared with the usual method: crushing the ice at low temperature under vacuum and measuring CO2 in the air of the opened bubbles, after removing water vapour over a cold trap.
    The third method is sublimating all ice under vacuum and cryogenic separation of all components. That gives the same result as for the second method in total CO2, but is used for isotope research, to avoid fractionation.

    Thus even if there was some migration into the (intercrystalline) ice structure, it is unmeasurable, as the comparison between the three methods shows. By far not enough to explain the disappearance of a quarter of the total amount out of the bubbles.

  88. Ferdinand says: That is certainly not true for the Vostok ice core.
    =================================================
    wrong
    Almost all of the common bacteria that occupy permanently cold environments have been isolated from Vostok ice cores. Most of that work was with Vostok ice cores exclusively.
    =================================================
    Ferdinand says:Which means that the population around dust is (far) higher than at other places.
    =================================================
    Which means that bacteria have mobility in ice.
    Which also means that you’re not looking at one type of bacteria that only feeds on one food.
    The ice you’re looking at was not always that deep and not always that cold.
    What happened to it before you got to it?
    ===================================================
    Ferdinand says:I don’t know which ice core you mean:
    ===================================================
    I’m talking about the ice cores that have elevated methane levels, the ones closest to the surface.
    Where the ice would be exposed to temp changes, seep, etc
    Where bacteria would be more able to produce methane.

    My concerns about Ice cores and bacteria are this.
    The oldest, deepest, ice cores show the highest CO2 levels.
    As ice cores get newer, they are closer to the surface, and show lower CO2 levels.

    That is exactly what goes on in another liquid environment that uses bacteria, marine sediments. Methane is produced at the aerobic/anaerobic interface.

    Stepping back and looking at ice cores, not from atmospheric levels being captured, but from a purely biological stand, it can all be explained biologically.

  89. David, I fear you have fallen into the same trap as another poster (where, I can’t recall). The signal you are finding is real. However, it is due to an unseen influence.

    We all know that it takes a while for the firn to close off entirely. How long? At high-snow sites, it’s not long, decades to a century or so. At Vostok, which is a low-moisture “frozen desert”, it takes much longer.

    So the difference between air age and ice age is critical at Vostok. To estimate the snowfall rate, the scientists use the changes in the d18O levels in the ice as a proxy for temperature. Higher temperature = more evaporation = more snowfall.

    Unfortunately, higher temperatures also mean more CO2. So you end up with a correlation between CO2 and ice age. Since the general assumption is that ice age is not a function of CO2, this can mess up your numbers subtly but badly.

    Second, if the diffusion rate were as high as you say, why do we find large differences in the CO2 content that are only a short distance apart? Difference of 3-5 ppmv per metre are common at Vostok, at an age of 300,000 years. If the ice can hold that differential for 300,ooo years, the diffusion rate must be really, really slow.

    Let’s suppose, for example, that CO2 concentration in the first ice bubbles was actually 100 ppmv different from the second ice bubbles when they were were laid down. That seems possible.

    For that to decay to 4 ppmv in 100,000 years, the decay rate would need to be 4 = 100 * X ^300000. Excel tells me that is .001% decline per metre per year.

    Let us suppose that the actual CO2 was say 400 ppmv 300,000 years ago, and on average it has been 1,500 metres deep over that time. Let us say it has been slowly equalizing with a background CO2 level of 275 ppmv. How much diffusion would we expect?

    Well, at .001% per metre per year, and 1500 metres on average, we’d expect a diffusion of .001% / 1,500 per year. If that were kept up for 300,000 years, we’d see a decay of … drum roll … wait for it … 0.2%.

    I’m sorry, but your post doesn’t pass the math test. Ice can retain a 3 – 5 ppmv differential per metre for three hundred thousand years …

  90. This diffusion issue is a valid and important point.

    I believe the diffusion effect also essentially exists in the other proxies, too, for a similar reason – that the ages of the data points in different proxies, and even within a proxy, are all approximations that are then muddled together when averaging and homogenizing. High frequency extremes are lost when one peak in one proxy study is shifted slightly from the high frequency extremes of other studies or other proxies. Each peak is accepted as having a discrete and precise time factor, but this precision is only imaginary, since each C14 (and most other types of) data point has a fairly sizable imprecision. (Most efforts in challenging the methodologies seems to have been aimed at the amplitude of the data, not the time factor.) Mis-timed peaks are fairly analogous to David’s diffusion, since the timing of the extremes do not match up.

    A primary residual of this is that high frequency extremes are reduced when multiple proxies are averaged. The averaging itself (as was noted on WUWT about 18 months ago) reduces the high frequency extremes. The time element/diffusion reduces them even further by essentially blending them.

  91. @Willis,

    1 meter ~ 1 year at Law Dome (late 19th to 20th centuries).
    1 meter ~ 100 years at Vostok (during last Pleistocene glaciation).
    1 meter ~ 1,000 years at Taylor Dome (during last Pleistocene glaciation).

    3-5 ppmv/m at Vostok is about 3-5 ppmv/century. 3-5 ppmv/m at Taylor Dome can be 3-5 ppmv/millenium. 3-5 ppmv at Law Dome is about 3-5 ppmv/yr.

    1 meter of “diffusion” at Law Dome is smoothing. 1 meter of “diffusion” at Taylor Dome (11-27kya) is a serious low-pass filter.

    I’ve now included Vostok back to 157 kya and Taylor Dome (11-27 kya) to the graph…

    CO2 v Sample Rate w/ Vostok

    When I included the older data, I found that the exponential trend-line was not a good fit; a logarithmic trend-line fit quite well.

    Then I plotted the GRIP (Greenland) data (8-40 kya) on the same graph…

    CO2 v Sample Rate w/ Vostok and GRIP

  92. stumpy says:
    January 2, 2011 at 1:43 pm
    Can the equation then be used in reverse to estimate what the co2 levels would have actually been once mixing etc… are accounted for? Would be very interesting to see the results, even if only indicative!

    The amplitude can be restored quite easily by a gain function. Surface consistent amplitude compensation processes are routinely used to boost the gain of seismic reflection data while preserving the relative amplitude relationships.

    I think that it might also be possible to restore some of the higher frequency content as well through the use of deconvolution and other forms of wavelet processing commonly used to improve the resolution of seismic reflection data.

    I’m going to run this idea by a friend of mine who runs the Dallas office of a seismic data processing company that specializes in this sort of thing. In many cases they can restore frequency content that traditionally was thought to have not been recorded.

  93. David Middleton says:
    January 4, 2011 at 1:45 am

    1 meter ~ 1 year at Law Dome (late 19th to 20th centuries).
    1 meter ~ 100 years at Vostok (during last Pleistocene glaciation).
    1 meter ~ 1,000 years at Taylor Dome (during last Pleistocene glaciation).

    3-5 ppmv/m at Vostok is about 3-5 ppmv/century. 3-5 ppmv/m at Taylor Dome can be 3-5 ppmv/millenium. 3-5 ppmv at Law Dome is about 3-5 ppmv/yr.

    First, sorry David that I have made a mistake by misinterpreting your “sample” rate, as literal sampling, not m/years…

    The interesting point is not the differences between different ice cores, but the changes in sampling rate within one core: Taylor Dome shows a sample rate starting as 10 years/meter and ends with 2,500 years/meter after 230,000 years at 550 meter depth.
    Vostok starts with 20 years/meter and ends with 540 years/meter at 3310 meter depth.
    Quite huge changes in sample rate with depth and quite huge differences between different ice cores.

    The Vostok ice core goes back 420,000 years with ups and downs of 100 ppmv in four cycles, with decreasing sample rate with depth. The interesting point is that there is a quite good correlation between the (ice based) temperature proxy (dD and d18O) and the (gas based) CO2 levels over the four cycles. If there was even the slightest diffusion, that would be visible over time as a fading away of the ratio. As an extra, that would be accellerated by the sample rate, as any diffusion would have the same speed over smaller layers (at the same temperature), representing much broader time periods. This is not the case at all, the ratio remains the same over 420,000 years (and recently confirmed over 800,000 years).
    And I like to see a sr/CO2 plot of the full 420,000 Vostok years (have no time now to do it myself)…

    Further, if there was diffusion over the first millennia (the Holocene), it would be strange to find such low levels: diffusion averages the levels over time, but it doesn’t change the average. That means that either the real levels at closing time were (much) lower or there was little migration…

  94. @ Ferdinand,

    If you plot that sample rate (I use m/yr rather than yr/m) against CO2 mixing ratio, you get a strong logarithmic correlation – Not just within individual cores; but across multiple cores (Law, Taylor, Vostok and GRIP) from the 20th century back to at least 157 kya (as far back as I’ve compiled sample rates)…

    CO2 v Sample Rate w/ Vostok and GRIP

    This is exactly the relationship that should exist if van Hoof’s theory that diffusion in the ice cores acts like a low pass filter is valid.

  95. Ferdinand Engelbeen says:
    January 3, 2011 at 11:17 am
    ….
    The temperature data from the Vostok borehole should be here:
    http://www.nature.com/nature/journal/v381/n6584/abs/381684a0.html
    but I don’t want to pay the scandalous sum they ask for an over 10 years old article.

    The data, at least, is available for free via http://www.ncdc.noaa.gov/paleo/icecore/antarctica/vostok/vostok_data.html .

    The assumptions behind the dating are crucial, but unfortunately are only discussed in the article.

  96. David Middleton says:
    January 4, 2011 at 6:31 am

    This is exactly the relationship that should exist if van Hoof’s theory that diffusion in the ice cores acts like a low pass filter is valid.

    Tom van Hoof was talking about the diffusion in the firn until bubble closing, not in the ice itself! The firn diffusion indeed acts as a low pass filter.

    I made a fast plot of Vostok alone (76-252 kyr), as that was the only one I could find fast with ice depth available for CO2: no trend at all. The same in your plot: the trend probably is the result of using different ice cores with different sr ratio, but similar CO2 level ranges…

  97. Hu McCulloch says:
    January 4, 2011 at 8:56 am

    The data, at least, is available for free via http://www.ncdc.noaa.gov/paleo/icecore/antarctica/vostok/vostok_data.html .

    The assumptions behind the dating are crucial, but unfortunately are only discussed in the article.

    Thanks Hu, I have looked there, but the “temperature” I did find was the reconstructed (hemispheric ocean) temperature, based on dD (or d18O). I am looking for the borehole temperature that the Russians have measured from the surface to the bottom of the drilling hole at Vostok (in preparation for an eventual drilling through the last ice to reach Lake Vostok).

  98. “”””” Ferdinand Engelbeen says:
    January 3, 2011 at 3:25 pm
    George E. Smith says:
    January 3, 2011 at 1:51 pm

    So you don’t like my usage of terms; so let me redefine; For OUT diffusion read IN diffusion; as in CO2 diffusing INTO THE ICE; which just co-incidently is diffusion OUT of the trapped air samples, INTO the cie walls around the air bubble; where rumor has it the CO2 abundance is much lower than in the air; hence the reason why Fick’s Law would be applicable; and my comment stands.

    Quite confusing, your use of IN and OUT, I must say… “””””

    How so confusing ? Clearly if something can pass IN to something, it clearly must simultaneously pass OUT of something else; there must be an interface to cross. And yes in the diffusion case, Fick’s law would dictate that the (net) flow of diffusant, will be in the direction from higher concentration towardws lower concentration. In fact of course the flow is both ways, as in evaporation for example; but the concentration gradient, and statistical mechanics results in a net drive in one direction; from high to low.

    You talk about diffusion as if there must be cracks or channels in the “solid” such as ice, for the CO2 or other gas to pass through; and passage will continue, until these defects are “corrected”, and sealed.

    Such things can exist, along grain boundaries of course; but the Physics of solid state semiconductor technology, demonstrates that no such avenues are needed. Few Crystals or solids, are as pure and defect free, as modern semiconductors, and the diffusion of impurities into them is well demonstrated and understood, despite the lack of grain boundaries or other structural defects.
    Impurity species diffuse interstitially, into a completely defect free structure; depending on the lattice and impurity species. The “intruders” may remain forever interstitial, or could in some cases be incorporated into the lattice itself.

    Now as to Joel’s dsecription; I take a lot of notice of his writings; and in the case under discussion; he most likely is very much more up to speed than I am; on the methodology and theory of CO2 and air entrapment in ice cores.

    Now basically, I pay little attention to those details, since I have never seen a complete blow by blow description of exactly where on earth the “air sample” and its CO2 was at the time it became incorporated into either liquid water of some ice crystal, or snow crystal, nor how it ultimately was transported to say, Antarctica, and Vostok in particular, and eventually deposited on the surface.

    I can tell you that in an article in Scientific American Journal for March 2005, A William F. Ruddiman (unknown to me) postulates that humans have been causing global warming for 8,000 years, and as a result heve stopped an ice age; presumably the one we were supposed to get in 1976.
    On page 52 of that issue, in that article, Ruddiman shows Carbon Dioxide data from two (Antarctic) ice cores, simply designated as ice core 1 and ice core 2; and they contain data going back for 2500 years. Well ice core 1 goes from 500 BC to about 1600 AD, while ice core 2 starts at 1000 AD and goes up to 1900 AD, so they overlap from 1000 AD up to 1600 AD; so 600 years of common proxy monitoring of atmospheric CO2 abundance (allegedly).

    Well the problem is, that during the 600 year overlap period; the two ice core records of atmospheric CO2 are nothing at all like each other and in fact from 1000 AD to 1200 AD the go in exactly the opposite directions, with # 2 rising very steeply and #1 falling at a good clipand then from 1400 AD to a600 AD #1 is rapidly rising, while #2 begins a steep plunge.

    Both are allegedly valid proxies for atmospheric CO2 and they tell two totally different stories with no possible meaningful commonality.

    So no; I do not understand the whole process of air sample entombment; nor the core recovery and ice and included air pockets treatmetn and quantitative analysis; to the extent that I believe Joel Shore, and you too do; and wouldn’t claim to; which is why I read what you guys write.

    But based on data from folks such as Dr Ruddiman; who I believe is well known for his work; I have about zero confidence, that these ice cores tell us much other than in the most gross manner, about the history of the earth atmosphere. I believe the Vostok and Dome C cores cover a history of seven or eight ice ages; or maybe that is eleven; and I suspect that earth orbit shifts are involved in those events; but I think it is specious to claim that recent decades or centuries of ice cores, are accurate depictions of the history of CO2 in the atmospehre.

    Take the Vostok cores for example; aren’t they somewhere in the range of 10,000 feet or so of ice; or at leas a couple of km.

    So that 800,000 year old ice from the vast depths. Was that laid down virtually on bedrock all those eons ago, while the atmospheric pressure was not too low; or was that laid down on km thickness of ice at 10,000 ft altitudes, and low atmospheric pressure, to be compressed and slowly sink as the bed rock contacting ice slowly melts, and runs away in never ending rivers.

    Like I say, I take what both of you say quite seriously; and in no way meant that Joel’s picture is quite wrong; simply that it is not all that clear cut; and there are arguments that can be made either way.

    Was it Einstein who said only a single experiment is required to falsify an incoreect theory; no matter how much supporting evidence there seems to be.

    Well Ruddiman’s ice cores #1 and #2 present such a contrary experimental result; that says ice core CO2 proxies are not dependable records of the global atmospheric CO2 abundance; and likely not for Temperature either.

  99. David Middleton says:

    I’ve now included Vostok back to 157 kya and Taylor Dome (11-27 kya) to the graph…

    CO2 v Sample Rate w/ Vostok

    When I included the older data, I found that the exponential trend-line was not a good fit; a logarithmic trend-line fit quite well.

    Then I plotted the GRIP (Greenland) data (8-40 kya) on the same graph…

    CO2 v Sample Rate w/ Vostok and GRIP

    But, we already know that your plot is completely devoid of meaning. What you are seeing is that there is a relationship between accumulation rate (which you misname “sample rate”) and what the CO2 level was. However, the reason for that relationship is:

    (1) For Law Dome vs. Taylor Dome, you are really just seeing the fact that Law Dome captures some of the modern industrial CO2 rise and Taylor Dome doesn’t.

    (2) For the others, you are seeing the fact that accumulation rate for some ice cores is strongly dependent on climate, with the accumulation rate being higher when the temperature is higher because a higher temperature generally results in more precipitation (and temperature and CO2 level are, of course, strongly correlated).

    So, your plot doesn’t really tell you anything about what you really want to know. It provides exactly zero evidence for what you claim to be showing evidence of. And, all the other available data (such as the paper that bubbagyro found) seems to imply that the effect of diffusion will range from completely negligible to maybe (in the very worst circumstances) about as large as the effects due to it taking time for the bubbles to close off.

  100. Dear Dr Middleton?

    Did you have a look on work by Dr Zbigniew Zaworowski (Poland) on CO2 Ice core analysis ; I believe he wrote several studies questioning the validity of this approach

  101. George E. Smith says:

    On page 52 of that issue, in that article, Ruddiman shows Carbon Dioxide data from two (Antarctic) ice cores, simply designated as ice core 1 and ice core 2; and they contain data going back for 2500 years. Well ice core 1 goes from 500 BC to about 1600 AD, while ice core 2 starts at 1000 AD and goes up to 1900 AD, so they overlap from 1000 AD up to 1600 AD; so 600 years of common proxy monitoring of atmospheric CO2 abundance (allegedly).

    Well the problem is, that during the 600 year overlap period; the two ice core records of atmospheric CO2 are nothing at all like each other and in fact from 1000 AD to 1200 AD the go in exactly the opposite directions, with # 2 rising very steeply and #1 falling at a good clipand then from 1400 AD to a600 AD #1 is rapidly rising, while #2 begins a steep plunge.

    George,

    Did you notice the scale on the vertical axis? The points from the two cores are **ALL** within 6ppm of each other! The majority are within about 2ppm of each other. Sure, if you are worried about measuring the CO2 concentration to a couple ppm that might be important…but I’ve never assumed that the ice core measurements are precise to that degree anyway! (After all, we know that there are some global and annual variations in CO2 levels on that scale.)

  102. George E. Smith says:
    January 4, 2011 at 12:16 pm

    You talk about diffusion as if there must be cracks or channels in the “solid” such as ice, for the CO2 or other gas to pass through; and passage will continue, until these defects are “corrected”, and sealed.

    Well, you understand the physics of diffusion of solids through solid matrices. You also know how much energy it costs to bring a few nanogram of a dope into the upper fraction of a mm from a silicon wafer. In the hope that the dope doesn’t migrate out of the matrix in the next decades (even not at elevated working temperature)… Thus how much CO2 do you think will migrate into the ice matrix at -40°C with a pressure equal for ice and gas? And how much will stay there (or migrate further)?

    Well the problem is, that during the 600 year overlap period; the two ice core records of atmospheric CO2 are nothing at all like each other and in fact from 1000 AD to 1200 AD the go in exactly the opposite directions, with # 2 rising very steeply and #1 falling at a good clipand then from 1400 AD to a600 AD #1 is rapidly rising, while #2 begins a steep plunge.

    Ruddiman’s thesis is well known, and was discussed at RC:
    http://www.realclimate.org/index.php/archives/2005/12/early-anthropocene-hyppothesis/
    I have no (free) access to the article, so can’t give much comment on the ice cores. But if you (or anyone) can send me the graphs, that will do. Or I will pay the reasonable $8.
    Seems strange to me, as I have a graph of all archived ice cores from Antarctica over the past 1,000 years:

    If the difference in the CO2 levels of Ruddiman’s graphs is within +/- 5 ppmv, that is within the range you find in all Antarctic ice cores for the same gas age. Most ice cores have a resolution that isn’t even fine enough to detect the difference between the MWP and LIA. Only the Law Dome (and another one, Siple Dome?) have enough resolution to show the cooling around 1600. That gives the impression of contradictory results, but it is just a matter of accuracy and resolution.

  103. daniel says:
    January 4, 2011 at 1:52 pm

    Did you have a look on work by Dr Zbigniew Zaworowski (Poland) on CO2 Ice core analysis ; I believe he wrote several studies questioning the validity of this approach

    Sorry, what Jaworowski says (the same invariable) themes since 1992 is completely outdated (by the work of Etheridge e.a., 1996 on the Law Dome ice cores), physically impossible (migration of CO2 from low to high levels) or completely wrong (he takes the ice age instead of the gas age for CO2 to compare that to atmospheric data).
    See further my comment on Jaworowski:
    http://www.ferdinand-engelbeen.be/klimaat/jaworowski.html

  104. “”””” Ferdinand Engelbeen says:
    January 4, 2011 at 3:15 pm
    George, my question is already answered by Joel… “””””

    Ferdinand, I’ll take a look at what Joel had to say regarding your question.

    As to the graphs Ruddiman presented in SA, don’t waste your $8.

    The actual P-P CO2 range of the two ice cores over the 2500 years; with 600 years of overlap , was from a low of 275 ppm for ice core # 2 at the 1600 end point of core #1 going to about 288ppm at 1900 for the same core.

    The #1 core ranged from 277 low 650 BC to a high of around 285 at 750 AD then dropped to 278 again around 1400 to top out at 283 at the 1600 end point.

    So maybe as you say; not outside the expected noise levels of those ice cores.

    But if so the question remains; where does Ruyddiman get off presneting this data to Scientific American, and its audience if it is all in fact phony baloney.

    If I take your caution; which I pay a lot of heed to; there is nothing whatsoever in ruddiman’s graph that he should even be writing about. He even attaches all knids of historical significance to events; whcih may be nothing more than noise, such as blaming the black death on what those ice cores “were doing”around 1350.

    Turns out that that is exactly the time period, when core #1 and core #2 tell their most totally different stories.

    And a Roman era plague that killed 25-40% of Europeans circa 570 AD corresponds to a wild vertical transient for core #1, while amazingly the black death of 1350 happens at the low of core #1.

    Evidently total BS of the highest order; but Ruddiman presents it as gospel truth for SA to swallow. I’m taking them at their word, that the december 2010 issue I received is the last one they will ever send me.

    Oh for an encore, Ruddiman takes the very first data point for core #1 at 750 BC and draws a straight line to the end point of core #2 at 1900 and calls that straight line the long term deforestation trend. Only three of the several dozen data points happen to lie above that line, and those three just barely so. Of course the two end points are by design exactly on that line.

  105. “”””” Joel Shore says:
    January 4, 2011 at 2:08 pm
    George E. Smith says:
    George,

    Did you notice the scale on the vertical axis? The points from the two cores are **ALL** within 6ppm of each other! The majority are within about 2ppm of each other. Sure, if you are worried about measuring the CO2 concentration to a couple ppm that might be important…but I’ve never assumed that the ice core measurements are precise to that degree anyway! (After all, we know that there are some global and annual variations in CO2 levels on that scale.)

    Well Joel; I don’t disagree with you or Ferdinad, one bit on that score; but don’t you think it is highly disingenuous for Ruddiman to present that apparently quite noisy and totally meaningless data, as if it was significant. It is quite misleading for SA and their readership.

    Now I trust you a whole lot more than that; to present meaningful input. I don’t have time or the energy to do my own independent ice core drilling; not am I that interested in the results; but I’m sure lots of folks are.

  106. George E. Smith says:

    As to the graphs Ruddiman presented in SA, don’t waste your $8.

    Oh for an encore, Ruddiman takes the very first data point for core #1 at 750 BC and draws a straight line to the end point of core #2 at 1900 and calls that straight line the long term deforestation trend. Only three of the several dozen data points happen to lie above that line, and those three just barely so. Of course the two end points are by design exactly on that line.

    George,

    I agree with you that that sidebar in the Scientific American article is very weak…and some of the claims (like a drop in CO2 around 500 AD) are just weirdly wrong. To be fair though, that is not the most central part of Ruddiman’s hypothesis and it also seems like a part that was messed up quite a bit in the translation between his original peer-reviewed article and the Sci Am popularization. Here is the original one: http://bill.srnr.arizona.edu/classes/182h/Climate/Ruddiman.pdf Note that Fig. 7 is the corresponding figure and it and the discussion of it are considerably better than the Sci Am article (e.g., he tells you where the data is from, he is more clear about the timing of various plagues etc, …) Probably the most important clarification is that the “deforestation trend” line that you objected to is clearly explained as being from other longer term data not shown, not simply from connecting the two points at the two ends of this graph. (See Fig. 2 for the data that was presumably used.)

    Anyway, I am not really trying to defend Ruddiman’s hypothesis (which I have no strong opinion either way on), and especially this particular aspect of it which really seems to be pushing the ice core data beyond its reliabability…but just wanted to point out that going to the original peer-reviewed source you do at least get a better picture of what he is trying to say.

  107. “”””” Joel Shore says:
    January 5, 2011 at 5:24 am
    George E. Smith says:

    As to the graphs Ruddiman presented in SA, don’t waste your $8. “””””

    Joel; thanks for the elucidation. But for the SciAm article, I would have no knowledge of either Ruddiman or his thesis. It’s nice that others have access to more dependable sources.

    But perhaps it is even more important that these authors get their story straight and square; when dealing with a more lay public such as the SciAm audience.

    So I am hoping that SA keep to their promise and send me no more issues of their magazine following the Dec 2010 issue; which they assure me is my last issue, after 40 years of continuous subscription plus 35 years of continuous gift subscription, for my former Tarpon and Bone Fishing guide in the Florida Keys. His issues will continue to arrive on schedule; untill I (or maybe he) ends up getting recycled to the atmosphere and environs.

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