Observed characteristics of Mozambique Channel eddies

• Published in: Journal of Geophysical Research: Oceans Vol. 115; no. C9
• Main Authors: Swart, N. C., Lutjeharms, J. R. E., Ridderinkhof, H., de Ruijter, W. P. M.
• Format: Journal Article
• Language: English
• Published: Washington, DC Blackwell Publishing Ltd 01.09.2010; American Geophysical Union
• Subjects: Anomalies; Boundaries; Channels; Earth sciences; Earth, ocean, space; Eddies; Exact sciences and technology; Geophysics; heat flux; Marine; Mozambique Channel; Nutrients; Oceans; Physical oceanography; Saline; salt flux; Satellite altimetry; Stations; Surface velocity; Water column; Indian Ocean; Kwazulu Natal; Southern Africa; Africa; Agulhas current; South Africa; Mozambique Channel; satellites; Water mass; salt; geologic sections; Space remote sensing; Satellite observation; velocity; chemically precipitated rocks; anomalies; evaporites; in situ; nutrients; Interannual variation; Cyclonic eddy; sedimentary rocks; channels; heat flux; Western boundary current; oxygen; heat transfer; Diameter; flow; altimetry
• ISSN: 0148-0227; 2169-9275; 2156-2202; 2169-9291
• DOI: 10.1029/2009JC005875

The flow in the Mozambique Channel is dominated by large, southward propagating, anti‐cyclonic eddies, as opposed to a steady western boundary current. These Mozambique Channel eddies feed their waters into the Agulhas Current system, where they are thought to have a significant influence on the formation of the Natal Pulse and Agulhas Ring shedding. Here we use in situ hydrographic and nutrient data, together with satellite altimetry and surface velocity profilers to provide a detailed characterization of the Mozambique Channel eddies. Two warm eddies in the Channel at 20°S and 24°S had diameters of over 200 km. They rotated anti‐cyclonically with a tangential velocity of over 0.5 m.s−1. Vertical sections show that the eddies reached to the bottom of the water column. Relative to the surrounding waters, the features were warm and saline. The total heat and salt anomalies for the southernmost eddy were computed relative to a reference station close by. At 24°S the total anomalies were 1.3 × 1020 J and 6.9 × 1012 kg, respectively, being on par with Agulhas rings. Mozambique Channel eddies thus have the potential to form a major contribution to the southward eddy heat flux in the Agulhas Current system. The feature also had positive nutrient and negative oxygen anomalies. The large magnitude of the water mass anomalies within the eddy suggests that interannual variability in Mozambique Channel eddy numbers would have a significant impact on downstream water mass characteristics.