Large-Scale Forcing of the Agulhas Variability: The Seasonal Cycle

In this article the authors examine the kinematics and dynamics of the seasonal cycle in the western Indian Ocean in an eddy-permitting global simulation [Parallel Ocean Circulation Model, model run 4C (POCM-4C)]. Seasonal changes of the transport of the Agulhas Current are linked to the large-scale circulation in the tropical region. According to the model, the Agulhas Current transport has a seasonal variation with a maximum at the transition between the austral winter and the austral spring and a minimum between the austral summer and the austral autumn. Regional and basin-scale mass balances indicate that although the mean flow of the Agulhas Current has a substantial contribution from the Indonesian Throughflow, there appears to be no dynamical linkage between the seasonal oscillations of these two currents. Instead, evidence was found that the seasonal cycle of the western Indian Ocean is the result of the oscillation of barotropic modes forced directly by the wind. 1