SeaWiFs observations of upwelling south of Madagascar: long-term variability and interaction with East Madagascar Current

Sea-viewing Wide Field-of-view Sensor data from September 1997 to November 2001 were used to observe upwelling south of Madagascar. From Empirical Orthogonal Function analysis, we found that the upwelling is enhanced in austral winter each year except 1999 and in austral summer each year except 2001. Current and wind stress are the mechanisms to cause the upwelling. The upwelling borders on the East Madagascar Current in the east and south. The movement and deformation of the boundary between the two contain the information of their interaction. Mechanism of the interaction can be explained by the shear wave propagation theory.