Testing of the Autonomous Microconductivity-Temperature Vehicle and a Direct Technique for the Determination of Turbulent Fluxes with Autonomous Underwater Vehicles

Abstract : Our long-term goal is to measure the horizontal variability of heat and salt flux in the upper ocean. This will allow us to study the turbulent boundary layer under non homogeneous forcing and the development of coherent boundary layer features such as rolls and Langmuir circulation. Our immediate objectives are to develop a technique to measure vertical water velocity and the turbulent fluxes of heat and salt with Autonomous Underwater Vehicles (AUV), and to construct a vehicle to fully test and exploit the technique. We have done this in a limited way with our Autonomous Conductivity and Temperature Vehicle (Morison and McPhee, 1997). We use the vertical motion of the ACTV as a proxy for the vertical motion of the water through which it moves. Comparison with other measurement techniques indicates this produces reasonable estimates of flux at the scales of convective turbulence. The key elements of the new technique will be to use all available guidance and control data and account for the dynamics of the vehicle in the estimation of vertical velocity. A new small AUV will be built for proving the technique. The new AUV is crucial for this because it will have an adequate sensor suite to fully measure the vehicle motion, and its configuration and control system will be optimally designed to determine vertical velocity.