Effect of internal tides on slow energy fluctuations of impulse signals in an experiment on a long-distance stationary path

Temporal energy fluctuations of impuse signals generated by powerful explosive sources of sound are considered by using the experimental data obtained on a long-distance stationary path in the northwestern Pacific. The signals were received on the Kamchatka shelf (a characteristic ocean depth of about 200 m) at two points spaced by 115 km in the latitudinal direction, one of the reception points being located on the shelf far from its edge, and the other, on the shelf edge. The signal radiation was performed in the deep ocean, at a distance of about 1000 km from the shelf edge. Charges were exploded every hour for more than five days. The frequency-dependent energy fluctuations of the signals and those of the first mode alone were measured in the frequency range 10–80 Hz. It is shown that the amplitudes of energy fluctuations of the first mode in narrow bands can exceed 10 dB and make the main contribution to the energy fluctuations of the total signal. The maximum energy of the first mode is reached on the high tide. It is hypothesized that internal tide-induced variations of the sound velocity field on the shelf affect the degree of energy interaction between the first mode and the bottom.