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Agulhas Ring Injection Into the South Atlantic During Glacials and Interglacials : Volume 5, Issue 1 (17/03/2008)

By Zharkov, V.

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Book Id: WPLBN0004021027
Format Type: PDF Article :
File Size: Pages 37
Reproduction Date: 2015

Title: Agulhas Ring Injection Into the South Atlantic During Glacials and Interglacials : Volume 5, Issue 1 (17/03/2008)  
Author: Zharkov, V.
Volume: Vol. 5, Issue 1
Language: English
Subject: Science, Ocean, Science
Collections: Periodicals: Journal and Magazine Collection, Copernicus GmbH
Publication Date:
Publisher: Copernicus Gmbh, Göttingen, Germany
Member Page: Copernicus Publications


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Zharkov, V., & Nof, D. (2008). Agulhas Ring Injection Into the South Atlantic During Glacials and Interglacials : Volume 5, Issue 1 (17/03/2008). Retrieved from

Description: Geophysical Fluid Dynamics institute, Florida State University, FL, USA. Recent proxies analysis 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 very good 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.

Agulhas ring injection into the South Atlantic during glacials and interglacials

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