Topic Area

The Variability of the Agulhas Retroflection

LCDR Brett S. Martiny, USN

1. Forms the southern part of the western boundary current system of the south Indian Ocean.
2. Source water from Mozambique Channel and the area east of Madagascar.
3. Flows southward alone the African coast until it overshoots the continent shelf and retroflects at about 17º E and flows eastward as the Agulhas Return Current along the Subtropical Convergence.
4. Sharp meander in the return current at about 27º E, which is identified as a cold core eddy.
5. Large eddy southwest of Cape Town, a significant meridional flux.
6. Meridional meanders in the return current lie predominantly at 27º E and 32º E, with a second retroflection location at 16º E.
7. Total retroflection lies between 20º E and 16º E
8. Western boundary of retroflection unclear.
9. A number of ring and eddylike features are associated with the Agulhas Retroflection.
10. Mean diameter of the retroflection loop is 342 km.
11. The mean rate of westward progradation is 12 cm/s and on an average, nine events per year, with each event lasting approximately 39 days.
12. At the conclusion of each event spawns the shedding of a warm-core Agulhas ring , average diameter of 307 km
13. Rings shed at the Agulhas retroflection westwards, rapidly losing their distinct surface thermal expression.
14. The Agulhas Retroflection and shedding of rings is analogous to similar features of other western boundary currents in the Southern Hemisphere but more intense.

Grundlingh, M. L., Observation of a large meander in the Agulhas Current, J. Geophys. Res., 84, 3776-3778, 1979.

Harris, T. F. W., and D. van Foreest,  The Agulhas Current in March 1969. Deep-Sea Res., 25, 549-561, 1978.

Legeckis, R., and Gordon, A. L., Indian-Atlantic transfer of thermocline water at the Agulhas Retroflection. Science, 227, 1030-1033, 1985.

Lutjeharms, J. R. E., The Agulhas Current system during the north-        east monsoon season, J. Phys. Oceanogr., 6, 665-670, 1976.

Lutjeharms, J. R. E., and D. J. Baker, A statistical analysis of the meso-scale dynamics of the southern ocean, Deep Sea Res., Part A, 27,145-150,1980.

Lutieharms, J. R. E., a: Spatial scales and intensities of circulation in the ocean areas adjacent to South Africa. Deep-Sea Res., 28, 1289-1302, 1981.

Lutieharms, J. R. E, b: Features of the southern Agulhas Current circulation from satellite remote sensing. S. Afr. J Sci., 77, 231-236, 1981.

Lutieharms, J. R. E., and R. C. van Ballegooyen, Topographic control in the Agulhas Current system. Deep-Sea Res., 31, 1321-1337, 1984.

Lutjeharms, J. R. E., and R. C. van Ballegooyen, Topographic control in the Agulhas Current system, Deep Sea Res., 31, 1321-1337, 1984.

Lutjeharms, J. R. E., and A. L. Gordon, Shedding of an Agulhas ring observed at sea, Nature, 325, 138-140, 1987.

Michaelis, G., Die Wasserbewegung an der Oberfldche des Indischen Ozeans im Januar und Juli, Veroeff. Inst. Meereskd. Univ. Berlin, A8, 1-32, 1923.

 

Paech, H., Die Oberfldchenstrbmungen um Madagaskar in ihrem

Jahrlichen Gang, Veroeff. Inst. Meereskd. Univ. Berlin, A16, 1-39, 1926.

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