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| Titel |
High-latitude obliquity as a dominant forcing in the Agulhas current system |
| VerfasserIn |
T. Caley, J.-H. Kim, B. Malaizé, J. Giraudeau, T. Laepple, N. Caillon, K. Charlier, H. Rebaubier, L. Rossignol, I. S. Castañeda, S. Schouten, J. S. Sinninghe Damsté |
| 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 (2011-11-26), S.1285-1296 |
| Datensatznummer |
250004687
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| Publikation (Nr.) |
 copernicus.org/cp-7-1285-2011.pdf |
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| Zusammenfassung |
| The Agulhas Current transport of heat and salt from the Indian Ocean
into the South Atlantic around South Africa (Agulhas leakage), can affect
the Atlantic meridional overturning circulation (AMOC) and, thus, influence
global climate. However, efforts to elucidate forcing mechanisms connecting
the Agulhas leakage with the upstream dynamics of the current have been
hampered by a lack of climate records extracted from the area where the
Agulhas current originates. We determine 800-kyr sea surface temperature
(SST) and salinity (SSS) records from the "precursor" region of the
Agulhas current and show that these records contain strong 100-kyr and
41-kyr cycles. This latter obliquity-driven cycle is nearly in phase with
changes in the annual mean insolation and air temperature at high southern
latitudes. In contrast, our SST and SSS records did not reveal
precession-driven cycles, which is surprising given the low-latitude
location of the upstream Agulhas current. Together, this indicates that the
dynamics of the Agulhas current system is mainly controlled by high latitude
obliquity through its influence on the position of the Southern Hemisphere
subtropical front (STF) and its associated westerlies. Our study
demonstrates that obliquity may drive an important part of the 100 kyr
cycles observed in the system rather than precession. Our results also
suggest that a stronger Agulhas current, associated with a northward shift
of the wind system during glacial periods, leads to reduced leakage, in
accordance with the theory. We argue that during terminations, stronger
Agulhas leakage of heat and salt was triggered by increased obliquity
exerting a positive feedback on the global climate system through modulating
long-term AMOC variations. |
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