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| Titel |
Warm Paleocene/Eocene climate as simulated in ECHAM5/MPI-OM |
| VerfasserIn |
M. Heinemann, J. H. Jungclaus, J. Marotzke |
| 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 ; 5, no. 4 ; Nr. 5, no. 4 (2009-12-15), S.785-802 |
| Datensatznummer |
250002705
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| Publikation (Nr.) |
 copernicus.org/cp-5-785-2009.pdf |
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| Zusammenfassung |
We investigate the late Paleocene/early Eocene (PE) climate using the
coupled atmosphere-ocean-sea ice model ECHAM5/MPI-OM. The surface in our
PE control simulation is on average 297 K warm and ice-free, despite a
moderate atmospheric CO2 concentration of 560 ppm. Compared to a pre-industrial
reference simulation (PR), low latitudes are 5 to 8 K warmer, while high
latitudes are up to 40 K warmer. This high-latitude amplification is in
line with proxy data, yet a comparison to sea surface temperature proxy data
suggests that the Arctic surface temperatures are still too low in our PE simulation.
To identify the mechanisms that cause the PE-PR surface temperature differences,
we fit two simple energy balance models to the ECHAM5/MPI-OM results. We find that
about 2/3 of the PE-PR global mean surface temperature difference are caused by a
smaller clear sky emissivity due to higher atmospheric CO2 and water vapour
concentrations in PE compared to PR; 1/3 is due to a smaller planetary albedo.
The reduction of the pole-to-equator temperature gradient in PE compared to PR
is due to (1) the large high-latitude effect of the higher CO2 and water
vapour concentrations in PE compared to PR, (2) the lower Antarctic orography,
(3) the smaller surface albedo at high latitudes, and (4) longwave cloud radiative
effects. Our results support the hypothesis that local radiative effects rather
than increased meridional heat transports were responsible for the "equable" PE climate. |
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