Acoustically Focused Oceanographic Sampling in Coastal Environments

A new oceanographic measurement concept, Acousti-cally Focused Ocean Sampling-AFOS, is presented, combining a tomographic network with small autonomous underwater vehicles. Using wireless local area network technology, the acoustic tomography data are recorded and processed in real time for achieving a low-resolution estimate of oceanographic parameters. The results are used to focus direct measurements by a network of small AUV's in areas of high spatial and temporal variability. By combining the high coverage but low resolution of the tomography with the high resolution capabilities of the AUVs, oceanographic phenomena with small scale dynamics controlled by large scale environmental forcing can be mapped. The feasibility of the new measurement concept has been demonstrated in a June 96 experiment in Haro Strait, BC, aimed at mapping coastal fronts driven by combined estuarian and tidal forcing.