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| Titel |
Agulhas ring injection into the South Atlantic during glacials and interglacials |
| VerfasserIn |
V. Zharkov, D. Nof |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1812-0784
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| Digitales Dokument |
URL |
| Erschienen |
In: Ocean Science ; 4, no. 3 ; Nr. 4, no. 3 (2008-09-30), S.223-237 |
| Datensatznummer |
250001760
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| Publikation (Nr.) |
 copernicus.org/os-4-223-2008.pdf |
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| Zusammenfassung |
Recent proxies suggest that, at the end of the last glacial, there was a
significant increase in the injection of Agulhas rings into the South
Atlantic (SA). This brought about a dramatic increase in the salt-influx
(from the Indian Ocean) into the SA helping re-start the then-collapsed
meridional overturning cell (MOC), leading to the termination of the Younger
Dryas (YD). Here, we propose a mechanism through which large variations in
ring production take place.
Using nonlinear analytical solutions for eddy shedding, we show that there are
restricted possibilities for ring detachment when the coast is oriented in
the north-south direction. We define a critical coastline angle below which
there is rings shedding and above which there is almost no shedding. In the
case of the Agulhas region, the particular shape of the African continent
implies that rings can be produced only when the retroflection occurs beyond
a specific latitude where the angle is critical. During glaciation, the wind
stress curl (WSC) vanished at a latitude lower than that of the critical
angle, which prohibited the retroflection from producing rings. When the
latitude at which the WSC vanishes migrated poleward towards its present day
position, the corresponding coastline angle decreased below the critical
angle and allowed for a vigorous production of rings.
Simple process-oriented numerical simulations (using the Bleck and Boudra
model) are in satisfactory agreement with our results and enable us to
affirm that, during the glacials, the behavior of the Agulhas Current (AC)
was similar to that of the modern East Australian Current (EAC), for which
the coastline slant is supercritical. |
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