The objective of this article is to present evidence for the existence of s
easonal variability in sea surface height (SSH) anomaly in the Agulhas Retr
oflection region. TOPEX/POSEIDON altimeter data. are used to estimate seaso
nal changes in the mesoscale SSH variability. There is a seasonal oscillati
on of SSH variability characterized by a maximum during the austral summer
and a minimum during the austral winter. The amplitude of this seasonal cha
nge is approximately 30% of its mean value. During the winter season the sp
atial distribution of SSH variability resembles that of the annual mean var
iability, with relative maxima centered at approximately 18 degrees E, 27 d
egrees E and 38 degrees E. During the summer there is an additional maximum
which extends from approximately 20 degrees E to 25 degrees E and from 40
degrees to 42 degrees S. Analysis of longitude-time diagrams reveals that a
t low latitudes planetary waves propagate freely throughout the basin. Alon
g the latitude of the Agulhas Retroflection region, the East Madagascar Rid
ge hampers the westward propagation of planetary waves. It is speculated th
at the difference between summer and winter patterns is caused by an inerti
ally driven bifurcation of the Agulhas Current.