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| Titel |
Limited response of peatland CH4 emissions to abrupt Atlantic Ocean circulation changes in glacial climates |
| VerfasserIn |
P. O. Hopcroft, P. J. Valdes, R. Wania, D. J. Beerling |
| 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 ; 10, no. 1 ; Nr. 10, no. 1 (2014-01-20), S.137-154 |
| Datensatznummer |
250116900
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| Publikation (Nr.) |
 copernicus.org/cp-10-137-2014.pdf |
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| Zusammenfassung |
| Ice-core records show that abrupt Dansgaard–Oeschger (D–O) climatic warming events
of the last glacial period were accompanied by large increases in the
atmospheric CH4 concentration (up to 200 ppbv). These abrupt changes
are generally regarded as arising from the effects of changes in the Atlantic
Ocean meridional overturning circulation and the resultant climatic impact on
natural CH4 sources, in particular wetlands. We use two different
ecosystem models of wetland CH4 emissions to simulate northern CH4
sources forced with coupled general circulation model simulations of five
different time periods during the last glacial to investigate the potential
influence of abrupt ocean circulation changes on atmospheric CH4 levels
during D–O events. The simulated warming over Greenland of 7–9 °C
in the different time periods is at the lower end of the range of
11–15 °C derived from ice cores, but is associated with strong
impacts on the hydrological cycle, especially over the North Atlantic and
Europe during winter. We find that although the sensitivity of CH4
emissions to the imposed climate varies significantly between the two
ecosystem emissions models, the model simulations do not reproduce sufficient
emission changes to satisfy ice-core observations of CH4 increases
during abrupt events. The inclusion of permafrost physics and peatland carbon
cycling in one model (LPJ-WHyMe) increases the climatic sensitivity of CH44
emissions relative to the Sheffield Dynamic Global Vegetation Model (SDGVM) model, which does not incorporate these
processes. For equilibrium conditions this additional sensitivity is mostly
due to differences in carbon cycle processes, whilst the increased
sensitivity to the imposed abrupt warmings is also partly due to the effects
of freezing on soil thermodynamics. These results suggest that alternative
scenarios of climatic change could be required to explain the abrupt glacial
CH4 variations, perhaps with a more dominant role for tropical wetland
CH4 sources. |
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