Upper Ocean Shear and Density Variability at the Equator during TROPIC HEAT

Abstract

Abstract A four and one-half day time series of upper-ocean shear and density observations was collected in the tropical Pacific Ocean in November 1984. The measurements were made on the equator at 139°50′W during a period when the equatorial undercurrent was well developed and 20–30 day period velocity fluctuations were prominent. Shear observations were collected with a ship-mounted acoustic-Doppler velocity profiler; density data were obtained from a loosely tethered microstructure instrument. The mean shear profile during the series strongly reflected the structure of the undercurrent; however, the meridional component contributed significantly to the magnitude of the total shear. The mean Richardson number was large near the undercurrent core, but fell to values less than 0.5 25 m above and below the core, and was below 0.25 in the upper 40 m for most of the sample period. Buoyancy frequency varied on a diurnal time scale in the upper 50 m owing to the solar heating cycle, but a compensating diurnal ...