Towed CTD (conductivity, temperature, and depth) chain measurements in the 2010 Philippine Sea experiment.

Abstract

The 2010 Philippine Sea Experiment cruise included two tows of the “towed CTD chain”, an 800‐m‐long, ship‐towed cable with 88 CTD sensor fins distributed along its length. The goal of this instrument’s use in the experiment was to obtain high‐resolution (in space and time) measurements of ocean conductivity and temperature in the upper 500–700 m of the deep‐ocean water column, in order to characterize the horizontal spatial statistics of internal waves and “spice” (density‐compensated sound‐speed fluctuations). The effects of such ocean variability upon acoustic variability in long‐range ocean acoustic propagation is an active area of current research. Despite technical difficulties with the system, measurements at 3–5 s sampling periods were obtained on one to three dozen sensors distributed over 700 m depth. The first tow was 93 km for about 39 h and the second tow was 124 km for about 30 h. These datasets will be validated and/or augmented by measurements from a Microcat CTD mounted on the bottom of the cable on each tow and a second mounted at mid‐cable during the second tow. A summary of the dataset and initial findings will be shown. [Work supported by ONR.]