Microstructure Patches in the Thermocline

Abstract Profiles of temperature microstructure have been found to exhibit strong intermittence in the distribution of χ, the rate of diffusive smoothing of temperature fluctuations. Records from the main thermocline in the subtropical gyro of the Pacific have been examined to determine the thickness of patches of microstructure activity. Since these profiles have few thermohaline intrusions, the small-scale structure must be generated by the “breaking” of internal waves or by salt fingering. The variations in the intensity of the microstructure thus reflect the irregularity in time and space of the occurrence of these processes. In addition, there is an intermittence of the microstructure due to variations in intensity of the microstructure within individual mixing events. Much of this internal variation is due to modulation of the amplitude of the microscale temperature fluctuations by the larger scale finestructure. In an attempt to compensate for the second type of intermittence, zero-crossings betwee...