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| Titel |
Response of methane emissions from wetlands to the Last Glacial Maximum and an idealized Dansgaard-Oeschger climate event: insights from two models of different complexity |
| VerfasserIn |
B. Ringeval, P. O. Hopcroft, P. J. Valdes, P. Ciais, G. Ramstein, A. J. Dolman, M. Kageyama |
| 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 ; 9, no. 1 ; Nr. 9, no. 1 (2013-01-23), S.149-171 |
| Datensatznummer |
250017430
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| Publikation (Nr.) |
 copernicus.org/cp-9-149-2013.pdf |
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| Zusammenfassung |
| The role of different sources and sinks of CH4 in changes in
atmospheric methane ([CH4]) concentration during the last 100 000 yr
is still not fully understood. In particular, the magnitude of the change in
wetland CH4 emissions at the Last Glacial Maximum (LGM) relative to the
pre-industrial period (PI), as well as during abrupt climatic warming or
Dansgaard–Oeschger (D–O) events of the last glacial period, is largely
unconstrained. In the present study, we aim to understand the uncertainties
related to the parameterization of the wetland CH4 emission models
relevant to these time periods by using two wetland models of different
complexity (SDGVM and ORCHIDEE). These models have been forced by identical
climate fields from low-resolution coupled atmosphere–ocean general
circulation model (FAMOUS) simulations of these time periods. Both emission
models simulate a large decrease in emissions during LGM in comparison to PI
consistent with ice core observations and previous modelling studies. The
global reduction is much larger in ORCHIDEE than in SDGVM (respectively
−67 and −46%), and whilst the differences can be partially explained by
different model sensitivities to temperature, the major reason for spatial
differences between the models is the inclusion of freezing of soil water
in ORCHIDEE and the resultant impact on methanogenesis substrate
availability in boreal regions. Besides, a sensitivity test performed with
ORCHIDEE in which the methanogenesis substrate sensitivity to the
precipitations is modified to be more realistic gives a LGM reduction of
−36%. The range of the global LGM decrease is still prone to
uncertainty,
and here we underline its sensitivity to different process
parameterizations. Over the course of an idealized D–O warming, the
magnitude of the change in wetland CH4 emissions simulated by the two
models at global scale is very similar at around 15 Tg yr−1, but this is only
around 25% of the ice-core measured changes in [CH4]. The two models
do show regional differences in emission sensitivity to climate with much
larger magnitudes of northern and southern tropical anomalies in ORCHIDEE.
However, the simulated northern and southern tropical anomalies partially
compensate each other in both models limiting the net flux change. Future
work may need to consider the inclusion of more detailed wetland processes
(e.g. linked to permafrost or tropical floodplains), other non-wetland
CH4 sources or different patterns of D–O climate change in order to be
able to reconcile emission estimates with the ice-core data for rapid
CH4 events. |
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