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| Titel |
Enrichment in 13C of atmospheric CH4 during the Younger Dryas termination |
| VerfasserIn |
J. R. Melton, H. Schaefer, M. J. Whiticar |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1814-9324
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| Digitales Dokument |
URL |
| Erschienen |
In: Climate of the Past ; 8, no. 4 ; Nr. 8, no. 4 (2012-07-19), S.1177-1197 |
| Datensatznummer |
250005706
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| Publikation (Nr.) |
 copernicus.org/cp-8-1177-2012.pdf |
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| Zusammenfassung |
| The abrupt warming across the Younger Dryas termination
(~11 600 yr before present) was marked by a large increase
in the global atmospheric methane mixing ratio. The debate over
sources responsible for the rise in methane centers on the roles of global
wetlands, marine gas hydrates, and thermokarst lakes. We present a
new, higher-precision methane stable carbon isotope ratio (δ13CH4) dataset from ice
sampled at Påkitsoq, Greenland that shows distinct
13C-enrichment associated with this rise. We
investigate the validity of this finding in face of known anomalous methane
concentrations that occur at Påkitsoq. Comparison with previously
published datasets to determine the robustness of our results indicates a
similar trend in ice from both an Antarctic ice core and previously
published Påkitsoq data measured using four different extraction and
analytical techniques. The δ13CH4 trend suggests that
13C-enriched CH4 sources
played an important role in the concentration increase. In a first attempt
at quantifying the various contributions from our data, we apply a methane
triple mass balance of stable carbon and hydrogen isotope ratios and
radiocarbon. The mass balance results suggest biomass burning (42–66%
of total methane flux increase) and thermokarst lakes (27–59%) as the
dominant contributing sources. Given the high uncertainty and low temporal
resolution of the 14CH4
dataset used in the triple mass balance, we also performed a mass balance
test using just δ13C and δD. These results further support biomass
burning as a dominant source, but do not allow distinguishing of thermokarst
lake contributions from boreal wetlands, aerobic plant methane, or termites.
Our results in both mass balance tests do not suggest as large a role for
tropical wetlands or marine gas hydrates as commonly proposed. |
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