ASA 129th Meeting - Washington, DC - 1995 May 30 .. Jun 06

2pUW29. Multiple ocean layering models and mode trapping in sublayers for high frequency propagation.

N. A. Sidorovskaia

Dept. of Phys., Univ. of New Orleans, New Orleans, LA 70148

M. F. Werby

Naval Res. Lab., Stennis Space Center, MS 39529

It is possible for sublayers in a layered ocean to have pronounced effects on the propagating modes in the water column. For example, atypical effects occur for sound speeds less than the overlaying water column or some overlying sublayers. In some cases one predicts the concentration of a large energy flux in that layer even at model eigenvalues that prohibit propagation in the water column while supporting propagating modes in the sublayer. Since some data suggest the possibility of underlying gaseous regions that support low sound speeds, this is a practical problem. This allows for the possibility that for a layer thick enough to absorb energy before arriving in a higher speed sublayer, the number of propagation modes in the water column can be reduced with increasing frequency. Since this is a frequency-dependent effect [effective (absorbing) thickness of layers is inversely proportional to wavelength or directly proportional to frequency], absorption into the overlying sublayers becomes more pronounced with increased frequency thus reducing the possibility of ``tunnelling'' which leads to a reduction in propagating modes in the water column. This effect is the converse of the usual case for ocean bottom layering and can be directly measured. Some interesting effects are studied and compared with available data using the high frequency mode model SWAMP. [Work sponsored by the Office of Naval Research.]