Fine-scale temperature variability: The influence of near-inertial waves


  • G. O. Marmorino,

  • L. J. Rosenblum,

  • C. L. Trump


Measurements made with a towed thermistor chain and acoustic doppler current profiler in the seasonal thermocline of the Sargasso Sea are examined for relationships among small-scale temperature “activity,” shear, and internal wave variability. Patches of intense activity measuring 5–10 m high and several kilometers in length are found to persist within a near-inertial wave packet. The packet was tagged with a drogue and followed for about 16 hours as it was advected along an edge of a cold-core ring. The patches occur along surfaces of high vertical shear, where the Richardson number (7-m vertical resolution) falls to values less than one. Within the patches are groups of small-scale internal waves and fluid overturns. The overturns are 1–3 m high and are associated with wave-breaking events. Away from the wave packet, activity levels are less, and the active fraction of the water column appears to be linked to variability in the internal wave field. It is conjectured that the near-inertial wave patches are the same species as persistent mixing patches observed by Gregg et al. (1986), which were also associated with a near-inertial wave.