Abstract: Turbulence Measurements from a Glider
Authors: Fabian Wollk, Rolf Lueck (Rockland Scientific Inc.), Lou St. Laurent (Florida State University)
Turbulence measurements are typically carried out from tethered free-fall profilers because they are driven by buoyancy, and provide a nearly vibration-free platform from which to measure the turbulent velocity shear, ∂u/∂z and ∂v/∂z.While profilers provide fast repetition of the measurement and real-time data display, they are also labor intensive and require dedicated ship operations and skilled personnel.
We present the results from a recent deployment of turbulence shear probes on a Slocum ocean glider — a vehicle that is also driven by buoyancy but can operate autonomously for long durations. The measurement package attached to the glider is small and neutrally buoyant, can be activated by the glider controller, record data for up to 35 days (continuous on time), and carries the usual suite of sensors — two shear probes, two fast-response thermistors, a pressure transducer, and a three-axis accelerometer. Tests in a small lake indicate that vehicle vibrations are small and that the shear probes can resolve dissipation rates as small 1x10-9 W kg-1, which is comparable to tethered free-fall profilers. Therefore, it will be possible to take long-duration of mixing without a proportional increase in cost and labor.