Estimates of Horizontal Divergence and Vertical Velocity in the Equatorial Pacific

Abstract

Horizontal divergence and vertical velocity in the surface mixed layer of the equatorial Pacific between 90° and 150°W are estimated from current measurements obtained from trajectories of freely drifting buoys during 1979?1990. The 12-year averaged horizontal divergence is predominantly meridional and has a maximum magnitude of 3?4 (? 10?6 s?1) in a 20-km-wide latitude band cantered on the equator. Using the equation of continuity, this divergence corresponds to an upwelling velocity of 1.5?2 (? 10?4 m s?1) at 50-m depth. The seasonal variations of equatorial divergence are in good agreement with the local zonal wind stress.