On the fast decay of Agulhas rings.

van Sebille, Erik, van Leeuwen, Peter Jan, Biastoch, Arne and de Ruijter, Wilhelmus P. M. (2010) On the fast decay of Agulhas rings. Open Access Journal of Geophysical Research: Oceans, 115 (C3). C03010. DOI 10.1029/2009JC005585.

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Abstract

The Indian Ocean water that ends up in the Atlantic Ocean detaches from the Agulhas Current retroflection predominantly in the form of Agulhas rings and cyclones. Using numerical Lagrangian float trajectories in a high-resolution numerical ocean model, the fate of coherent structures near the Agulhas Current retroflection is investigated. It is shown that within the Agulhas Current, upstream of the retroflection, the spatial distributions of floats ending in the Atlantic Ocean and floats ending in the Indian Ocean are to a large extent similar. This indicates that Agulhas leakage occurs mostly through the detachment of Agulhas rings. After the floats detach from the Agulhas Current, the ambient water quickly looses its relative vorticity. The Agulhas rings thus seem to decay and loose much of their water in the Cape Basin. A cluster analysis reveals that most water in the Agulhas Current is within clusters of 180 km in diameter. Halfway in the Cape Basin there is an increase in the number of larger clusters with low relative vorticity, which carry the bulk of the Agulhas leakage transport through the Cape Basin. This upward cascade with respect to the length scales of the leakage, in combination with a power law decay of the magnitude of relative vorticity, might be an indication that the decay of Agulhas rings is somewhat comparable to the decay of two-dimensional turbulence.

Document Type: Article
Keywords: Oceanography; Agulhas Current; ocean circulation
Research affiliation: OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-TM Theory and Modeling
OceanRep > The Future Ocean - Cluster of Excellence
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1029/2009JC005585
ISSN: 2169-9275
Projects: Future Ocean
Expeditions/Models/Experiments:
Date Deposited: 22 Nov 2010 10:57
Last Modified: 16 Jan 2018 13:39
URI: http://oceanrep.geomar.de/id/eprint/10057

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