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| Titel |
Methane variations on orbital timescales: a transient modeling experiment |
| VerfasserIn |
T. Y. M. Konijnendijk, S. L. Weber, E. Tuenter, M. Weele |
| 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 ; 7, no. 2 ; Nr. 7, no. 2 (2011-06-17), S.635-648 |
| Datensatznummer |
250004522
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| Publikation (Nr.) |
 copernicus.org/cp-7-635-2011.pdf |
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| Zusammenfassung |
| Methane (CH4) variations on orbital timescales are often associated with
variations in wetland coverage, most notably in the summer monsoon areas of
the Northern Hemisphere. Here we test this assumption by simulating
orbitally forced variations in global wetland emissions, using a simple
wetland distribution and CH4 emissions model that has been run on the output of a
climate model (CLIMBER-2) containing atmosphere, ocean and vegetation
components. The transient climate modeling simulation extends over the last
650 000 yr and includes variations in land-ice distribution and greenhouse
gases. Tropical temperature and global vegetation are found to be the
dominant controls for global CH4 emissions and therefore atmospheric
concentrations. The relative importance of wetland coverage, vegetation
coverage, and emission temperatures depends on the specific climatic zone
(boreal, tropics and Indian/Asian monsoon area) and timescale (precession,
obliquity and glacial-interglacial timescales). Despite the low spatial
resolution of the climate model and crude parameterizations for methane
production and release, simulated variations in CH4 emissions agree well
with those in measured concentrations, both in their time series and
spectra. The simulated lags between emissions and orbital forcing also show
close agreement with those found in measured data, both on the precession
and obliquity timescale. We find causal links between atmospheric CH4
concentrations and tropical temperatures and global vegetation, but only
covariance between monsoon precipitation and CH4 concentrations. The primary
importance of the first two factors explains the lags found in the CH4
record from ice cores. Simulation of the dynamical vegetation response to
climate variation on orbital timescales would be needed to reduce the
uncertainty in these preliminary attributions. |
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