Shallow Water Tomography

Abstract

The tomogaphic approach with reciprocal transmission has been applied to a shallow water area in the Florida Straits to give a direct observation of range and depth averaged currents and temperatures. Such spatial averages are not easily obtained with conventional current measurement methods. The propagation models and inversion methods of deep ocean tomography cannot be directly applied to shallow water locations since the spread in arrival times amongst paths is inherently limited in shallow propagation channels and the interaction with the rough ocean bottom can cause further uncertainty in path identification and travel time measurements. Nevertheless, acoustic reciprocal transmission experiments have been successful in the Florida Straits. Acoustic measures are interpreted with ray theory and parabolic equation propagation models to give averaged currents and temperatures which are in good agreement with measurements with current meter arrays. The experimental approach, inversion methods and equipment requirement are considered for the Florida Straits experiment and for applictions to other shallow water areas. The precision and limitations of the method are discussed.