The knowledge of salinity in a specific sea area with high accuracy is required to solve several acoustic and hydrophysical problems on the ocean shelf. Unlike temperature, which can be measured continuously for a long time, with, for example, thermistor strings (thermostrings), salinity values of required accuracy can be obtained only using CTD profiling. This is why methods of estimating salinity from temperature could be helpful. In this paper, the authors propose using the regression method for solving this type of problem and demonstrate the efficiency of this method using examples of temperature measurements from anchored thermostrings. For the correct construction of regressions, the authors analyzed the errors of CTD measurements and suggested a method for the dynamic correction of raw CTD data. From CTD profiling datasets of 12 years (2011–2022), after their dynamic correction, the authors obtained regression polynomial formulas for calculating salinity from temperature and studied data stability in space and time at the hydrophysical test site, located in the shelf zone of the Sea of Japan. The authors consider this method efficient and applicable in solving a variety of acoustic and hydrophysical problems.

This paper presents a discussion on observations of nonlinear internal waves (NLIWs) in the coastal zone of the Sea of Japan, based on the mooring of thermostring clusters in different seasons of 2022. For statistical evaluation of the frequency of event occurrence and determination of NLIW movement direction, we use our observations of the past 12 years. We present the NLIW structures, observed in spring, summer, and autumn of 2022, which are typical for this shelf area. Two types of nonlinear waves are described—solitary and undular bores, with or without strong vertical mixing behind the front. We demonstrate spatial transformation of an undular bore as it moves over the shelf. A mathematical model based on the second-order shallow water approximation is proposed for numerical simulation. To simplify calculations, the authors limit themselves to two- and three-layer shallow water models. We investigate the possibility of spatiotemporal reconstruction of internal nonlinear structures between thermostrings using experimental data and proposed models. The authors show that at distances of up to several kilometers between thermostrings, the wave fields of strongly nonlinear and nonstationary structures can be successfully reconstructed. Water flow induced by NLIWs can be reconstructed from the data of even one thermostring.

In this paper, the authors present and analyze the geoacoustic digital seabed model they developed, which is a digital description of the water column characteristics, seabed topography, and information about sediments and rocks (their composition and elastic properties) for Peter the Great Bay, the Sea of Japan. The model consists of four relief layers, a foundation and three layers of bottom sediments, and also contains the velocities of longitudinal waves in rocks and statistical characteristics of the sound velocity distribution in the water layer for three seasons. Acoustic characteristics of geological structures are based on seismoacoustic studies, sediment lithology, and laboratory measurements of rock samples collected onshore. The velocities of longitudinal and transversal waves and also the density of the sediments were calculated from their empirical dependencies on the granulometric composition of bottom sediment samples over an area of about 800 km². In a limited area of the shelf (approximately 130 km²), high-frequency acoustic studies were carried out using echo sounders, and the longitudinal wave velocities of the top sedimentary layer were determined. Porosity, density, longitudinal, and transverse wave velocities in bottom sediments were calculated using empirical models with a normal coefficient of reflection from the seabed. A comparison was made of the results of calculating the elastic properties of the seabed using various methods.