Barnola, Jean Marc
Brook, Edward J.
- We undertook an interlaboratory comparison of techniques used to extract and
analyze trapped gases in ice cores. The intercomparison included analyses of standard
reference gases and samples of ice from the Greenland Ice Sheet Project 2 (GISP2) site.
Concentrations of CO₂, CH₄, the δ¹⁸O of O₂, the δ¹⁵N of N₂, and the O₂/N₂, and Ar/N₂ ratios
were measured in air standards and ice core sampries. The standard reference scales for CO₂
and CH₄ were consistent at the ±2% level. The δᴼ²/N₂ and δ¹⁸O of O₂ measurements showed
substantial deviations between the two laboratories able to measure these ratios. The
deviations are probably related to errors associated with calibration of the working standards.
The δᴬʳ/N₂ and δ¹⁵N of N₂ measurements were consistent. Five laboratories analyzed the
CH₄ concentration in a 4.2-m section of the GISP2 ice core. The average of 20 discrete CH₄
measurements was 748±10 parts per billion by volume (ppbv). The standard deviation of
these measurements was close to the total analytical uncertainty associated with the
measurements. In all cases, those laboratories employing a dry extraction technique
determined higher CH₄ values than laboratories using a wet extraction technique. The origin
of this difference is unclear but may involve uncertainties associated with blank corrections.
Analyses of the CO₂ concentration of trapped gases showed extreme variations which cannot
be explained by analytical uncertainties alone. Three laboratories measured the [CO₂] on 21
discrete depths yielding an average value of 283±13 parts per million by volume (ppmv). In
this case, the standard deviation was roughly a factor of 2 greater than the analytical
uncertainties. We believe the variability in the measured [CO₂] results from impurities in the
ice which may have compromised the [CO₂] of trapped gases in Greenland ice.
- Sowers, T., et al. (1997), An interlaboratory comparison of techniques for extracting and analyzing trapped gases in ice cores, Journal of Geophysical Research, 102(C12), 26,527–26,538, doi:10.1029/97JC00633.
|Funding Statement (additional comments about funding)
- Support for T.A.S. was derived from NSF-OPP grant 93-21558. Ice core research at URI was supported by grants from the U.S. National Science Foundation. E.J.B. was also supported by a NOAA Climate and Global Change postdoctoral fellowship. Participation of D.M.E. in the intercomparison as supported in part by funding from the Australian Department of Environment, Sport and Territories (DEST) through the National Greenhouse Core Research Program.
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- Vol. 102 no. C12
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- Journal of Geophysical Research