Path and variability of the Agulhas Return Current

The combined analysis of hydrographic, kinematic, and dynamic data collected during the 1997–1999 KAPEX (CAPe of Good Hope EXperiments) reveals a quasi-stationary meandering pattern of the Agulhas Retroflection Current east and upstream of the Southwest-Indian Ridge. The current meanders between 38°S and 40°S in a spatially and temporally continuous fashion and has a core width of approximately 70 km with an associated transport of 44±5×106 m3 s−1 in the upper 1000 m. Peak surface velocities decrease from 2.1 m s−1 near the Agulhas Retroflection to 1.1 m s−1 around 32°E. Meander troughs (northward extremes) are found predominantly near 26.8°E, 32.6°E and 38.9°E, while crests (southward extremes) are located with high probability near 29.7°E, 35.5°E and 42.9°E, resulting in a typical wavelength of 500 km. Cold eddies are shed along the northern boundary of the current from meander troughs into the recirculation regime between the Agulhas Current proper and the Agulhas Return Current. Strongest cyclonic eddies are preferably shed in austral autumn. The cyclonic eddies so formed propagate westward at an average phase-speed of 5.4 cm s−1, with, however, a variability of at least the same magnitude. Subsequently, the cyclones are absorbed by the next meander trough located upstream and to the west of the shedding trough.