HIGH-FREQUENCY INTERNAL WAVES AT 0-DEGREES, 140-DEGREES-W AND THEIR POSSIBLE RELATIONSHIP TO DEEP-CYCLE TURBULENCE

An analysis of a moored time series at 0 degrees, 140 degrees W from N ovember to December 1991 found a nighttime enhancement of isotherm dis placement variance and of zonal velocity variance below the surface mi xed layer at frequencies higher than 1 cph. The nighttime enhancement was generally not seen below the core of the equatorial undercurrent. At 45-m depth, the potential energy and the horizontal kinetic energy of high-frequency waves were strongly correlated and similar in magnit ude. The shear production of turbulence kinetic energy calculated from the mooring measurements is strongly correlated with the turbulence k inetic energy dissipation rate observed from the nearby R/Vs Wecoma an d Moana Wave during the Tropical Instability Wave Experiment. This sug gests a dynamical link between the observed high-frequency internal wa ves and deep-cycle turbulence. The relationship between internal waves and turbulence in the thermocline was further explored in a case stud y of one energetic wave packet. This wave packet propagated westward a nd downward with a horizontal wavelength of no less than 200 m. The po tential energy was similar to the horizontal kinetic energy of the wav e packet, with the dominant variance occurring in a frequency band clo se to the local buoyancy frequency. The estimated vertical flux of the horizontal momentum of waves during the event was 0.3 Pa, three times the surface wind stress. About 2 hours after the wave packet passed t he mooring site, an anomalous turbulence dissipation rate with a magni tude similar to that of the estimated shear production of the wave pac ket was observed from the R/V Wecoma. The observed time lag was likely the result of the spatial separation of the observing platforms.