Anomalous surface currents in the tropical Indian Ocean

An anomalous climate event occurred in 1997 in the Indian Ocean with severe consequences for the surrounding continental areas. In response to an inte nsification of the trade winds, a westward gradient of SST and an anomalous reversal of the eastward surface currents with peak velocity anomalies exc eeding 1 m/s were evident in boreal autumn. A similar but weaker event took place in 1994. In this study we examine the observational record during th e 1990s including surface drifter velocities, SST and altimeter sea level t o confirm these dramatic changes. We examine the key momentum balance betwe en wind-induced momentum flux and the pressure gradient force as well as th e important role of horizontal temperature advection in the mixed layer hea t response.