On Variations of the Sound Signal Propagation Time under a Stationary Ice Cover

Abstract—In experiments on a stationary acoustic track under a solid ice cover, estimates of possible sound signal propagation time variations at distances of ∼4 km with a period of more than 100 s were obtained. The experiments were carried out on Lake Baikal in the spring period, when the vertical profile of the sound speed has two sections characteristic of freshwater areas: an upper layer with a near constant sound speed and a lower layer with linear growth of sound speed. Under these conditions, the variations of the propagation time did not exceed ~10^–4 s. Numerical modeling showed that the variations of propagation times due to the variability of the medium are minimal for the case when the sound source and receiver are located in the upper layer. It is demonstrated that in this case it is acceptable to take the sound speed in the upper quasi-homogeneous layer as the effective value of the sound speed, which determines the propagation time. The obtained results allowed us to formulate recommendations on under-ice acoustic positioning of autonomous underwater vehicles.