Eddy Energetics in the Upper Equatorial Pacific during the Hawaii-to-Tahiti Shuttle Experiment

Abstract

Abstract Eddy energetics in the central equatorial Pacific Ocean is examined using Acoustic Doppler Current Profiler velocities and CTD densities collected during the Hawaii-to-Tahiti Shuttle Experiment, in 1979–80. Three distinct sources of eddy energy are identified with varying degrees of statistical reliability, and are interpreted as evidence for three separate instabilities of the mean flow field. An instability at and just north of the equator occurs primarily in boreal summer and fall. It arises from the cyclonic shear between the Equatorial Undercurrent and the South Equatorial Current (SEC) north of the equator. The instability is present only when and where both currents are well developed, and there is little involvement of the shear between the SEC and the North Equatorial Countercurrent (NECC). The instability is characterized by local maxima in zonal and meridional eddy velocity variance, strong U*V* Reynolds stress, and large mean flow to eddy kinetic energy conversion. Despite seasonal va...