Secular trend in the near-surface currents of the equatorial Pacific Ocean

Abstract

The westward zonal near-surface currents of the equatorial Pacific Ocean appear to have strengthened during the past 20 years by 9-10 cm/s. Here we document this change in both near-surface drifter and moored currents. Accompanying this increase in surface currents is a shallowing of the equatorial thermocline and a weakening of the zonal component of the equatorial trade winds. However, a simple model suggests that the most important factor is a reduction by 8 m of the average mixed layer depth over this period.