Observations of Philippine Sea sound-speed perturbations, and the contributions from internal waves and tides, and spicy thermohaline structure

In the PhilSea09 pilot study two moorings equipped with temperature (T), conductivity (C), and pressure sensors, along with upper ocean ADCP, monitored ocean variability for a month in the Spring. The measurements reveal an energetic and nonlinear mixed diurnal-semidiurnal internal tide, a diffuse Garrett-Munk (GM) type internal wave field at or above the reference GM energy level, and a strong eddy field. One mooring, which was equipped with pumped sensors for enhanced salinity (S) resolution, was able to accurately quantify T and S variability along isopycnals (spice). The spice contribution to sound-speed fluctuation is observed to be strong near the mixed layer but significantly weaker than the other contributions in the main thermocline. Frequency spectra as well as vertical covariance functions will be presented to quantify the temporal and vertical spatial scales of the observed fluctuations.