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| Titel |
Steps towards a continuous methane concentration record back to 100 kyr BP |
| VerfasserIn |
T. Blunier, J. Chappellaz, S. Schuepbach, Ch. Stowasser, E. Brook, J. Rosen, R. Dallmayr, O. Pascual, M. Bigler, D. Leuenberger |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250063476
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| Zusammenfassung |
| Since the early 1980’s methane concentrations are measured from ice cores. Air is extracted
from individual ice samples by dry or wet extraction techniques and traditionally measured
by gas chromatography. Over the past decades a CH4 record has been achieved with sample
resolutions of down to decades and typical uncertainties of ±10 ppbv. Methane variations on
time scales of decades to millennia show important correlations with climate proxies in ice
cores, with remarkable correspondence between stable isotope records from Greenland ice
cores and methane concentrations during the last ice age. Recent developments allow
measurements of CH4 concentration directly on the drill site with very high resolution. In the
frame of the NEEM (NW Greenland) ice core drilling project we measured methane
concentration with a continuous flow analysis (CFA) system. The air in the CFA melt stream
is extracted with a hydrophobic membrane unit, dried, and routed through two
optical systems in series. The resolution of the methane data is unprecedented with
excellent precision. However, the accuracy of the data is not satisfactory due to
solubility of the gas in the melt stream and calibration issues. We combine precise off
line measurements from several Greenland ice cores with the on line NEEM CH4
record in order to obtain an improved Greenland CH4 composite record. Further
we establish a gas time scale for the NEEM ice core by synchronizing the CH4
records. |
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