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| Titel |
Upper ocean climate of the Eastern Mediterranean Sea during the Holocene Insolation Maximum – a model study |
| VerfasserIn |
F. Adloff, U. Mikolajewicz, M. Kucera, R. Grimm, E. Maier-Reimer, G. Schmiedl, K.-C. Emeis |
| 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 (2011-10-21), S.1103-1122 |
| Datensatznummer |
250004677
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| Publikation (Nr.) |
 copernicus.org/cp-7-1103-2011.pdf |
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| Zusammenfassung |
Nine thousand years ago (9 ka BP), the Northern Hemisphere experienced
enhanced seasonality caused by an orbital configuration close to the minimum
of the precession index. To assess the impact of this "Holocene Insolation
Maximum" (HIM) on the Mediterranean Sea, we use a regional ocean general
circulation model forced by atmospheric input derived from global
simulations. A stronger seasonal cycle is simulated by the model, which shows
a relatively homogeneous winter cooling and a summer warming with
well-defined spatial patterns, in particular, a subsurface warming in the
Cretan and western Levantine areas.
The comparison between the SST simulated for the HIM and a reconstruction
from planktonic foraminifera transfer functions shows a poor agreement,
especially for summer, when the vertical temperature gradient is strong. As a
novel approach, we propose a reinterpretation of the reconstruction, to
consider the conditions throughout the upper water column rather than at a
single depth. We claim that such a depth-integrated approach is more adequate
for surface temperature comparison purposes in a situation where the upper
ocean structure in the past was different from the present-day. In this case,
the depth-integrated interpretation of the proxy data strongly improves the
agreement between modelled and reconstructed temperature signal with the
subsurface summer warming being recorded by both model and proxies, with a
small shift to the south in the model results.
The mechanisms responsible for the peculiar subsurface pattern are found to
be a combination of enhanced downwelling and wind mixing due to strengthened
Etesian winds, and enhanced thermal forcing due to the stronger summer
insolation in the Northern Hemisphere. Together, these processes induce a
stronger heat transfer from the surface to the subsurface during late summer
in the western Levantine; this leads to an enhanced heat piracy in this
region, a process never identified before, but potentially characteristic of
time slices with enhanced insolation. |
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