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| Titel |
Glacial fluctuations of the Indian monsoon and their relationship with North Atlantic climate: new data and modelling experiments |
| VerfasserIn |
C. Marzin, N. Kallel, M. Kageyama, J.-C. Duplessy, P. Braconnot |
| 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 ; 9, no. 5 ; Nr. 9, no. 5 (2013-09-12), S.2135-2151 |
| Datensatznummer |
250085222
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| Publikation (Nr.) |
 copernicus.org/cp-9-2135-2013.pdf |
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| Zusammenfassung |
| Several paleoclimate records such as from Chinese loess, speleothems or
upwelling indicators in marine sediments present large variations of the
Asian monsoon system during the last glaciation. Here, we present a new
record from the northern Andaman Sea (core MD77-176) which shows the
variations of the hydrological cycle of the Bay of Bengal. The
high-resolution record of surface water δ18O dominantly reflects
salinity changes and displays large millennial-scale oscillations over the
period 40 000 to 11 000 yr BP. Their timing and sequence suggests that
events of high (resp. low) salinity in the Bay of Bengal, i.e. weak (resp.
strong) Indian monsoon, correspond to cold (resp. warm) events in the North
Atlantic and Arctic, as documented by the Greenland ice core record. We use the IPSL_CM4 Atmosphere-Ocean coupled General
Circulation Model to study the processes that could explain the
teleconnection between the Indian monsoon and the North Atlantic climate. We
first analyse a numerical experiment in which such a rapid event in the North
Atlantic is obtained under glacial conditions by increasing the freshwater
flux in the North Atlantic, which results in a reduction of the intensity of
the Atlantic meridional overturning circulation. This freshwater hosing
results in a weakening of the Indian monsoon rainfall and circulation. The
changes in the continental runoff and local hydrological cycle are
responsible for an increase in salinity in the Bay of Bengal. This therefore
compares favourably with the new sea water δ18O record presented
here and the hypothesis of synchronous cold North Atlantic and weak Indian
monsoon events. Additional sensitivity experiments are produced with the LMDZ
atmospheric model to analyse the teleconnection mechanisms between the North
Atlantic and the Indian monsoon. The changes over the tropical Atlantic are
shown to be essential in triggering perturbations of the subtropical jet over
Africa and Eurasia, that in turn affect the intensity of the Indian monsoon.
These relationships are also found to be valid in additional coupled model
simulations in which the Atlantic meridional overturning circulation (AMOC)
is forced to resume. |
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