Small-scale structure of temperature, salinity and sound speed off Southern California

A series of vertical profiles of temperature, salinity and sound speed were made from a surface vessel, using an STD/SV environmental profiling system in water 350 m deep off Southern California. The data were recorded digitally on magnetic tape at 0.2 Hz sample rate. Hydrographic casts were also made to obtain independent measurements of salinity, temperature and depth. The salinity obtained from the STD/SV is higher than that found using the hydrographic cast data. This difference appears to have a depth dependence but its nature cannot be clearly established from the present observations. There is also a hysteresis effect in the profiles of the properties measured and is, in part, attributed to internal waves. The presence of internal waves was established during this period from an independent set of temperature measurements, using a vertical thermistor array. The sound speed measured by the STD/SV was compared with the calculated sound speeds using the Anderson, the Frye and Del Grosso sound speed equations and the salinity and temperature data obtained by the STD/SV. The calculated sound speed is found to average 0.35 m/sec higher than the measured sound speed, using the Anderson and Frye equations.