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| Titel |
Oxygen stable isotopes during the Last Glacial Maximum climate: perspectives from data–model (iLOVECLIM) comparison |
| VerfasserIn |
T. Caley, D. M. Roche, C. Waelbroeck, E. Michel |
| 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. 6 ; Nr. 10, no. 6 (2014-11-10), S.1939-1955 |
| Datensatznummer |
250117073
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| Publikation (Nr.) |
 copernicus.org/cp-10-1939-2014.pdf |
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| Zusammenfassung |
We use the fully coupled atmosphere–ocean three-dimensional model of
intermediate complexity iLOVECLIM to simulate the
climate and oxygen stable isotopic signal during the Last Glacial Maximum
(LGM, 21 000 years). By using a model that is able to explicitly simulate
the sensor (δ18O), results can be directly
compared with data from climatic archives in the different realms.
Our results indicate that iLOVECLIM
reproduces well the main feature of the LGM climate in the atmospheric and
oceanic components. The annual mean δ18O in
precipitation shows more depleted values in the northern and southern high
latitudes during the LGM. The model reproduces very well the spatial
gradient observed in ice core records over the Greenland ice sheet. We
observe a general pattern toward more enriched values for continental
calcite δ18O in the model at the LGM, in
agreement with speleothem data. This can be explained by both a general
atmospheric cooling in the tropical and subtropical regions and a reduction
in precipitation as confirmed by reconstruction derived from pollens and
plant macrofossils.
Data–model comparison for sea surface temperature indicates that
iLOVECLIM is capable to satisfyingly simulate the
change in oceanic surface conditions between the LGM and present. Our
data–model comparison for calcite δ18O allows
investigating the large discrepancies with respect to glacial temperatures
recorded by different microfossil proxies in the North Atlantic region. The
results argue for a strong mean annual cooling in the area south of
Iceland and Greenland between the LGM and present (> 6 °C),
supporting the foraminifera transfer function reconstruction but in
disagreement with alkenones and dinocyst reconstructions. The data–model
comparison also reveals that large positive calcite δ18O anomaly in the Southern Ocean may be explained by
an important cooling, although the driver of this pattern is unclear. We
deduce a large positive δ18Osw anomaly for
the north Indian Ocean that contrasts with a large negative δ18Osw anomaly in the China Sea between the LGM and the
present. This pattern may be linked to changes in the hydrological cycle
over these regions.
Our simulation of the deep ocean suggests that changes in δ18Osw between the LGM and the present are not spatially
homogeneous. This is supported by reconstructions derived from pore fluids in
deep-sea sediments. The model underestimates the deep ocean cooling thus
biasing the comparison with benthic calcite δ18O data. Nonetheless, our data–model comparison
supports a heterogeneous cooling of a few degrees (2–4 °C) in the LGM
Ocean. |
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