Characterization of a warm-cored agulhas ring travelling south of the subtropical front

Vianello, Patrick

Characterization of a warm-cored agulhas ring travelling south of the subtropical front

Thesis / Dissertation

2010

Abstract

The south-eastern sector of the Atlantic Ocean near the South African coast is a region of high eddy activity in the form of Agulhas rings. These Agulhas rings play a vital role in the Inda-Atlantic inter-ocean exchange, and are critical for the global thermohaline circulation since these rings, spawned from the Agulhas retroflection, are typically of Indian Ocean origin. The pathway and behaviour of these Agulhas rings are affected by the underlying topography of the region with special reference to the Agulhas ridge and the Erica and Schmitt-Ott seamounts. This study investigates an Agulhas ring, which was identified during the Bonus-Goodhope cruise in February 2008. In addition to the hydrographic data obtained during this cruise, satellite data such as altimetry and Sea Surface Temperature (SST) are also employed to analyse and determine the origins of the feature, its development and lifespan. The majority of Agulhas rings remain within the Subtropical domain, however during the 2008 Goodhope cruise a positive anomaly was observed south of the Subtropical Front in the Subantarctic zone. Studying these features which drift into the Subantarctic domain may be important in understanding the global heat and salt budget since these Agulhas rings have positive heat and salt anomalies with respect to the surrounding region. Overall, it can be concluded that the Subantarctic zone had a major impact on the core properties of the ring such as its mixed layer depth and that the underlying topography such as the Agulhas ridge had a major effect on the behaviour and life span of the ring.

Keywords

Oceanography

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