Shallow water tracking in the sea of Nazare.

M.B. Porter
Dep. of Applied Mathematics
New Jersey Institute of Technology, NJ, USA
Y. Stephan
X. Demoulin
Centre Militaire d'Oceanographie - SHOM
Brest, France
S.M. Jesus
UCEH - Universidade do Algarve, Faro, Portugal
E. Coelho Instituto Hidrografico
Lisboa, Portugal

Comments: download pdf file .
Ref.: in Undersea Technology'98, IEEE Ocean Engineering Society, Tokyo, Japan, 1998.

Abstract: In the summer of 1996, an experiment was conducted off the coast of Portugal to study the effects of internal tides on sound propagation. This experiment - called INTIMATE'96 (Internal Tide Investigation by Means of Acoustic Tomography Experiments) - has provided a great deal of insight about the variability of pulse transmission over space and time. In contrast to a common view of shallow-water propagation as complicated and unpredictable, we find a steady pattern of echoes. The echo-pattern stretches and shrinks in a systematic way with the tides and allows us to infer the components of the first oceanographic modes. We also used the echo-pattern to track the source over a perido of several days. During this period the isotherms in the ocean wavered by 20 m as a result of the tides, providing a challenge for model-based tracking. We will discuss these acoustic results with emphasis on the source tracking.

ACKNOWLEDGMENT: this work was partially supported by PRAXIS XXI program under project 2./2.1/MAR/1695/95.