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| Titel |
The Middle Miocene climate as modelled in an atmosphere-ocean-biosphere model |
| VerfasserIn |
M. Krapp, J. H. Jungclaus |
| 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. 4 ; Nr. 7, no. 4 (2011-11-08), S.1169-1188 |
| Datensatznummer |
250004681
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| Publikation (Nr.) |
 copernicus.org/cp-7-1169-2011.pdf |
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| Zusammenfassung |
| We present simulations with a coupled atmosphere-ocean-biosphere model for
the Middle Miocene 15 million years ago. The model is insofar more
consistent than previous models because it captures the essential
interactions between ocean and atmosphere and between atmosphere and
vegetation. The Middle Miocene topography, which alters both large-scale
ocean and atmospheric circulations, causes a global warming of 0.7 K
compared to present day. Higher than present-day CO2 levels of 480 and
720 ppm cause a global warming of 2.8 and 4.9 K. The associated water
vapour feedback enhances the greenhouse effect which leads to a polar
amplification of the warming. These results suggest that higher than
present-day CO2 levels are necessary to drive the warm Middle Miocene
climate, also because the dynamic vegetation model simulates a denser
vegetation which is in line with fossil records. However, we do not find a
flatter than present-day equator-to-pole temperature gradient as has been
suggested by marine and terrestrial proxies. Instead, a compensation between
atmospheric and ocean heat transport counteracts the flattening of the
temperature gradient. The acclaimed role of the large-scale ocean circulation
in redistributing heat cannot be supported by our results. Including full
ocean dynamics, therefore, does not solve the problem of the flat temperature
gradient during the Middle Miocene. |
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