Any effect of trace hydrocarbons is instrument dependent.

The simplest method of CO2 analysis, which was alluded to by ZJ is an FID with a methanizer. The methanizer converts CO2 to CH4 and the FID measures carbon equivalents. This assumes that all carbonaceous gases are CH4. Thus a mole of C2H6 (ethane) would be detected as 2 moles of CH4, a mole of C3H8 would be detected as 3 moles of CH4, and so on.

Other more sophisticated analyzers would separate the components either by mass number or chromatography. A GC-FID/methanizer train would still count CH4 and CO2 as the same peak, however heavier hydrocarbons would have their own peaks. A mass spec would separate the components. NDIR, FTIR or laser based instruments would work as long as there were no interferences.

A new study has appeared which found new biota in ice which produce aromatic hydrocarbons.

Now what does that imply for the reliability of ice core measurements of trace carbon gases?

EXO LIFE
Life In Ice

L. Benning (Leeds) monitors sterile conditions in an ice coring tool. Credit: Kjell Ove Storvik/AMASE.for Astrobiology Magazine
Moffett Field CA (SPX) Oct 11, 2005
“We tested equipment that we are developing to look for life on Mars and discovered a rare and complex microbial community living in blue ice vents inside a frozen volcano,” remarked Hans E.F. Amundsen of Physics of Geological Processes (PGP) at the University of Oslo, Norway, and leader of the international AMASE team.

AMASE, the Arctic Mars Analog Svalbard Expedition, is designing devices and techniques to find life on Mars. Their test ground is Svalbard, (Norway) an area with a geology that is analogous to some Martian geology. “The instruments detected both living and fossilized organisms, which is the kind of evidence we’d be searching for on the Red Planet,” he continued.

Science leader of AMASE, Andrew Steele of the Carnegie Institution’s Geophysical Laboratory, explained that “ice-filled volcanic vents, such as these, are likely to occur on Mars and may be a potential habitat for life there.”

The carbonate rocks found within the approximately 1-million-year-old Sverrefjell volcano on Svalbard are similar to carbonate rosettes found in the Martian meteorite ALH84001 and may have been produced by common processes. The blue ice, trapped in the volcanic vents, may represent samples of water that formed identical carbonate deposits in the Sverrefjell volcano.

The scientists detected living and fossilized microbiota, in the ice and on the surfaces and cracks of other volcanic rocks, using their integrated life-detection strategy successfully tested by AMASE in 2004. “Our instrument, designed by scientists at the Jet Propulsion Lab (JPL), detected minute quantities of aromatic hydrocarbons from microorganisms and lichens present in the rocks and ice,” said Arthur Lonne Lane of JPL who made his 2nd voyage with the AMASE team.

Steele’s team from Carnegie deployed a suite of instruments to detect and characterize low levels of microbiota. “We performed several successful tests with a miniaturized instrument fitted with special protein microarray chips,” says Steele. “Our results showed that we were able to maintain sterile sampling procedures without introducing contamination from humans.”

Coring of the blue-ice vents and surface glacial ice involved developing a detailed procedure for sterilization of the ice-coring tool.

“The organisms found in ice are survivors! Small ecosystems in the ice have apparently adapted to extremely cold conditions,” says Liane Benning, University of Leeds. The ice and rock samples will be characterized further in labs at the Carnegie, the Smithsonian Institution, PGP, Penn State, and University of Leeds.

This summer’s AMASE expedition also involved interdisciplinary studies of the world’s northern-most thermal springs above sea level, rock weathering and pattern formation, and biota in glacial ice by the physicists, geologists, chemists, and biologists on the team. The AMASE group sampled sedimentary rocks that are roughly 780 million-year-old, which contain remarkable remains of microbial structures that still maintained morphologic structure.

“These rocks hold potential chemical markers of fossilized life. If there is similar evidence in ancient rocks on Mars, our equipment will be able to find it,” says Marilyn Fogel, biogeochemist and astrobiologist at Carnegie.

http://www.spacedaily.com/news/life-05zzzzzzp.html

there have been a lott of doubling experiments already going on for more then a decade right now, a lott of species seem to show a response under higher CO2 conditions….however, the response is species specific…..! e.g. my oak species do not go farther then 320 ppmv…..another problem which has to be taken into consideration with regards to reconstruction…therefore the multi-species approach…btw if anybody has access to leaf material from the FACE experiments……..we are always very much interested!

one general problem with most doubling studies I know is the usage of seedlings… they act different then adults..and you have to watch out to use them for calibration purposes…

about temperature….temperature is hardly an issue, some experiments with birch trees seem to give somewhat of a response but we are talking about temperature changes in multiple degrees celcius now..and the first response of a tree to temperature (regarding leaf development)lies in phenology, so the leaves start to develop earlier in the season if temperature rises…. the effect that can have an effect on stomatal frequency in general is water availability..this effects the amount of cell stretching in the epidermal cells..and so the density of the stomata…. therefore we use the index value between the number of stomata and the number of epidermal cells..this seems so far to be the most sensitive to CO2 changes

I wonder how they calibrate for the volcano?

Thank you for an excellent summary.

I agree that stomata are giving an indication that CO2 levels have changed both up and down during the past thousands of years. I have a high degree of confidence in the Mauna Loa CO2 data since they are using a Siemens NDIR located at the collection site. With 4 samples per hour, and frquent calibrations, the people at the site would quickly be aware of any instrument malfunctions or drift.

Most of the other CO2 collection points send periodic grab samples to Scripps for analysis. These samples could be impacted by diffusional effects, depending on the length of time they are en route to the NDIR at Scripps. These effects are likely to be small compared to the potential impacts of contamination and gas sample loss in ice cores.

Regarding John’s post, I agree that it would not be very difficult to set up a low CO2 stomata study in a green house. It would be possible to do it in a smaller enclosure, however a larger space is easier to control.

I forgot to ask: how sensitive are stomatal frequencies to temperature?

You’ve got plenty of greenhouses in the Netherlands…is it not possible to seal a few up from the atmosphere and run some CO2 sensitivity tests on something you do have a lot of: spagnum (sp?) moss or something else which is commonly found in the Netherlands?

As a response to the comments about our firn densification smoothing study. We were just curious how big the effect of firn densification smoothing in ice cores actually was and if this alone could explain the difference in amplitude we observed. It seemed that the smoothing was bigger then expected and for a large part could explain this discrepancy.

The Co2 wiggle during the thirteenth century AD has been recorded now in two ice cores and two (maybe three) stomatal frequency records… I agree that more accurate calibation of the stomata records is needed, however that these trees pick up this signal at all (various sites : north-sweden, the netherlands, west-coast USA) is for me evidence that this perturbation should at least have been higher than the absolute maximum of 12 ppmv suggested by the ice cores, I think we provided some evidence that this is partly caused by an underestimation of firn densification based smoothing (note: on these small timescales!),…

furthermore… a study by Gerber et al (2003), did a climate model run with a higher variability of air-temperatures then suggested by the hockey-stick scenario, and found out that this would have generated CO2 wiggles of up to 20 ppmv…..conclusion: ice core records do not record such changes during the past millennium so air-temperature variability is constrained….Now that several studies start to question the low-variability of air temperature changes during the past millennium, maybe we should also re-reconsider CO2 variability…if you do not believe the stomata evidence…this model study provide independent evidence that under higher T variabilities CO2 fluctuations should have been higher

Tom van Hoof

btw here’s some of the references of chapters from my thesis

Wagner, F., Kouwenberg, L.L.R., Van Hoof, T.B. & Visscher, H. (2004). Reproducibility of Holocene atmospheric CO2 records based on stomatal frequency analysis. Quaternary Science Reviews, 23/18-19, 1947-1954

Van Hoof, T.B., Kaspers, K.A., Wagner,F., Van de Wal, R.S.W., Kürschner, W.M. and Visscher, H. (2005) Atmospheric CO2 during the 13th century AD, reconciliation of data from ice core measurements and stomatal frequency analysis. Tellus B, 57/4, 351-355. doi 10.1111/j1600-0889.2005.00154

I am not hand waving. This is a circular argument. A proves B because B proves A.

When I calibrate an analytical instrument, I prefer to use a multipoint calibration with an NIST tracable standard blended by means of a blender which is calibrated for flow using a positive displacement cylinder. I calibrate the instrument over its full dynamic range. Lacking this, I at least do a zero and a span with a tracable standard. Of course in the case of zero and span calibrations, you must assume that the response is linear.

Here we have a system with no zero, thus a methodical approach would be a multipoint calibration through the full range of stomata indices and CO2 levels. The problem is that we do not have sufficient reliable data to do the calibration.

When I said that I could draw any calibration curve I desired through what is essentially a single point, I was trying to be humorous. If you only have a single point, or a couple of points on one end of the scale, you simply can not perform a calibration.