Mode coupling and redistribution of the sound intensity over depth at downslope propagation, in the area of thermocline's contact with bottom

Downslope propagation of the sound signal is studied in a coastal wedge when the temperature profile reveals the strong thermocline. Sound source is placed above the thermocline near the point of thermocline contact with bottom (TC point). Depth dependence of the sound intensity is considered far enough from the coastal line as a function of distance to the source. It is shown that for some position of the source between TC point and the coast, remarkable redistribution of the sound intensity over water depth takes place (sound field is stressed to the bottom). Numerical simulations of this phenomenon are carried out using adiabatic and coupled normal mode decomposition for bottoms with different sound speeds. Results of modeling are compared with the data of experiment in Lake Kinneret, where coastal slope is characterized by variation of depth from the coast to the 40 m at the distance about 8 km and sound speed profile with the thermocline at 20 m depth. Chirp signals with the center frequency 600 Hz were received by the vertical line array (VLA). Vertical distribution of the sound intensity along VLA was measured. Variability in accordance with theoretical model is demonstrated. [Work was supported by ISF.]