Mixed-Layer Shear Generated by Wind Stress in the Central Equatorial Pacific

Abstract

Sixteen months of wind and current profile observations in the central equatorial Pacific show the response of the upper-ocean shear to local wind forcing. The shear at the ocean surface is significantly correlated with the wind stress in direction but not in magnitude, implying that the vertical eddy viscosity coefficient is proportional to the square of the wind speed or to the stress. Using this variable eddy viscosity coefficient in Stommel's model of the Equatorial Undercurrent, we calculate shears in the mixed layer that compare well with the observations. The flow is downwind on the equator and tends toward and Ekman spiral off the equator.