New equations for sea water density calculation based on measurements of the sound speed

TL;DR

This paper introduces new equations to calculate seawater density using temperature, pressure, and sound speed, eliminating the need for direct salinity measurements, with applications in both technical and scientific contexts.

Contribution

The authors developed novel equations that estimate seawater density from sound speed, temperature, and pressure, bypassing the challenging salinity measurement.

Findings

First equation achieves RMS deviation of 0.062 kg/m3.

Second, more precise equation achieves RMS deviation of 0.0018 kg/m3.

Applicable for wide and narrow oceanographic parameter ranges.

Abstract

Density is one of the most important properties of seawater and is used in various marine research and technology. Traditionally, in the practice of oceanographic research, it is customary to con-sider density as a dependent parameter, which is a function of several other parameters taken as independent. Usually the following three parameters are used as the independent parameters: temperature, hydrostatic pressure and salinity. The issues of temperature and hydrostatic pressure measuring in situ are technologically well developed, while in the salinity measuring there are still unsolved problems. This is due to the fact that salinity is such a property that it is simply impossi-ble to determine directly in situ. To eliminate the problems associated with measurements of sa-linity, the authors developed the special new kind equation. That equation of the new kind ex-press the density of sea water through independent and in situ measured parameters: temperature, hydrostatic pressure and sound speed. The novelty of this approach is that using of the sound speed as the independent parameter makes it possible to exclude measurements of salinity. The authors developed two such new equations for the different cases of using. The first new equa-tion is intended for use in technical applications and reproduces the sea water density in a wide range of the aquatic environment parameters with a root mean square deviation of 0.062 kg/m3. The second more precise new equation is intended for scientific applications and reproduces the sea water density in a narrower oceanographic range of parameters with a root mean square devi-ation of 0.0018 kg/m3.