MicroSoar: A New Instrument for Measuring Microscale Turbulence from Rapidly Moving Submerged Platforms

A new high-frequency turbulence measuring instrument, MicroSoar, has been developed, tested, and used to make scalar variance dissipation rate measurements. MicroSoar was mounted on the undercarriage of SeaSoar, a depth-programmable winged platform, and towed by a ship, at speeds up to 7 kt, in a depth range of the sea surface to 120 m. Sensors carried by MicroSoar were a fast thermistor, a pressure sensor, a microscale capillary conductivity sensor, and a three-axis accelerometer. With appropriate assumptions about the local T–S relation, measurements of microscale conductivity fluctuations can often be used to directly determine temperature variance dissipation rate (xT), the Cox number (Cx), and the scalar diathermal turbulent diffusivity (KT). Compared to conventional quasi-free-fall tethered vertically profiling instruments, MicroSoar’s major advantage lies in its ability to sample large fluid volumes and large geographic areas in a short time, and to provide, rapidly and simply, two-dimensional (horizontal–vertical) representations of the distribution of oceanic mixing rates. 1