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| Titel |
Constraining global methane emissions and uptake by ecosystems |
| VerfasserIn |
R. Spahni, R. Wania, L. Neef, M. Weele, I. Pison, P. Bousquet, C. Frankenberg, P. N. Foster, F. Joos, I. C. Prentice, P. Velthoven |
| 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 ; 8, no. 6 ; Nr. 8, no. 6 (2011-06-23), S.1643-1665 |
| Datensatznummer |
250005962
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| Publikation (Nr.) |
 copernicus.org/bg-8-1643-2011.pdf |
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| Zusammenfassung |
| Natural methane (CH4) emissions from wet ecosystems are an
important part of today's global CH4 budget. Climate affects
the exchange of CH4 between ecosystems and the atmosphere by
influencing CH4 production, oxidation, and transport in the
soil. The net CH4 exchange depends on ecosystem hydrology,
soil and vegetation characteristics. Here, the LPJ-WHyMe global
dynamical vegetation model is used to simulate global net CH4
emissions for different ecosystems: northern peatlands
(45°–90° N), naturally inundated wetlands
(60° S–45° N), rice agriculture and wet mineral
soils. Mineral soils are a potential CH4 sink, but can also be
a source with the direction of the net exchange depending on soil
moisture content. The geographical and seasonal distributions are
evaluated against multi-dimensional atmospheric inversions for
2003–2005, using two independent four-dimensional variational
assimilation systems. The atmospheric inversions are constrained by
the atmospheric CH4 observations of the SCIAMACHY satellite
instrument and global surface networks. Compared to LPJ-WHyMe the
inversions result in a~significant reduction in the emissions from
northern peatlands and suggest that LPJ-WHyMe maximum annual emissions
peak about one month late. The inversions do not put strong
constraints on the division of sources between inundated wetlands and
wet mineral soils in the tropics. Based on the inversion results we
diagnose model parameters in LPJ-WHyMe and simulate the surface exchange
of CH4 over the period 1990–2008. Over the whole period we
infer an increase of global ecosystem CH4 emissions of
+1.11 Tg CH4 yr−1, not considering potential
additional changes in wetland extent. The increase in simulated
CH4 emissions is attributed to enhanced soil respiration
resulting from the observed rise in land temperature and in
atmospheric carbon dioxide that were used as input. The long-term
decline of the atmospheric CH4 growth rate from 1990 to 2006
cannot be fully explained with the simulated ecosystem
emissions. However, these emissions show an increasing trend of
+3.62 Tg CH4 yr−1 over 2005–2008 which can
partly explain the renewed increase in atmospheric CH4
concentration during recent years. |
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