A method of turbulence measurements from a moored reciprocating vertical profiler based on buoyancy-driven

Turbulence plays a crucial role in ocean dynamics and global biogeochemical cycles through redistributing heat, salt and nutrients across isodensity surfaces. Conventionally, most of microstructure measurements were conducted with vertical freefall profilers. In order to provide both a very high resolution vertical distribution of turbulent quantities and the long term series, a novel instrument MRVP (moored reciprocating vertical profiler) is developed in this paper. Recently, the instrument was deployed in the South China Sea (SCS) at 20° 55.490' N 118° 09.830' E for ocean turbulence measurements. The Profiler equipped with shear sensors, standard CTD sensors, and an attitude sensor measuring heading, pitch, roll, and three-axis acceleration, so that the Profiler is capable of measuring ocean microstructure. By changing the relationship between buoyancy and gravity, MRVP can make reciprocating sink and rise measurements along a moored smooth cable. Therefore, the MRVP can be moored at one place and autonomously acquires long-term microstructure series. The maximum measuring depth of the profiler can reach to 3000 meters. The dissipation rate in this experiment is between 10-9 and 10-7 W/kg, and matches well with Nasmyth spectrum in both shape and level. In general, the moored reciprocating vertical profiler (MRVP) offers a low-noise platform and a novel method suitable for multi-scale and longterm vertical ocean turbulence measurements.