Phytoplankton pigment distribution from SeaWiFS data in the subtropical convergence zone south of Africa:: a wavelet analysis

The Agulhas system (Agulhas Current, Retroflection, Agulhas Return Current (ARC)), south of Africa, constitutes a complex energetic system subject to high frequency mesoscale and low frequency variability. Using chlorophyll pigment concentration data collected by the SeaWiFS ocean color sensor and sea surface height satellite data, we demonstrate the utility of wavelet analysis in jointly analyzing ocean color and altimetric signals. Two distinct dynamical scenarios of the Agulhas system (October 1997 and January 1998) yield different dominant wavelengths (620 and 500 km) for the ARC Rossby wave. They are simultaneously retrieved from the chlorophyll and sea level anomaly signals. Longitudinal extension of the power, resulting from the wavelet analysis, also depends on the dynamical regime.