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| Titel |
High-resolution interpolar difference of atmospheric methane around the Last Glacial Maximum |
| VerfasserIn |
M. Baumgartner, A. Schilt, O. Eicher, J. Schmitt, J. Schwander, R. Spahni, H. Fischer, T. F. Stocker |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 9, no. 10 ; Nr. 9, no. 10 (2012-10-16), S.3961-3977 |
| Datensatznummer |
250007331
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| Publikation (Nr.) |
 copernicus.org/bg-9-3961-2012.pdf |
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| Zusammenfassung |
| Reconstructions of past atmospheric methane concentrations are
available from ice cores from both Greenland and Antarctica. The
difference observed between the two polar methane concentration
levels represents a valuable constraint on the geographical location of the methane sources. Here
we present new high-resolution methane records from the North
Greenland Ice Core Project (NGRIP) and the European Project for Ice
Coring in Antarctica (EPICA) Dronning Maud Land (EDML) ice cores
covering Termination 1, the Last Glacial Maximum, and parts of the
last glacial back to 32 000 years before present. Due to the
high resolution of the records, the synchronisation between the ice cores
from NGRIP and EDML is considerably improved, and the interpolar
concentration difference of methane is determined with unprecedented
precision and temporal resolution. Relative to the mean methane
concentration, we find a rather stable positive relative interpolar
difference throughout the record with its minimum value of
3.7 ± 0.7 % between 21 900–21 200 years before present, which
is higher than previously estimated in this interval close to the
Last Glacial Maximum. This implies that Northern Hemisphere boreal
wetland sources were never completely shut off during the peak
glacial, as suggested from previous bipolar methane concentration records. Starting at 21 000 years before present, i.e. several
millennia prior to the transition into the Holocene, the relative
interpolar difference becomes even more positive and stays at
a fairly stable level of 6.5 ± 0.8 % during Termination 1.
We thus find that the boreal and tropical methane sources increased by approximately the same factor during Termination 1.
We hypothesise that latitudinal shifts in the Intertropical Convergence Zone (ITCZ) and the monsoon system
contribute, either by dislocation of the methane source regions or, in case
of the ITCZ, also by changing the relative atmospheric volumes of the
Northern and Southern Hemispheres, to the subtle variations in the relative
interpolar concentration difference on glacial/interglacial as well as on
millennial time scales. |
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