On the development of regional scales of practical salinity and equations of state of sea water

Zaburdaev V. I.

     It is known that the practical salinity scale SHPS-1978 and the equation of state US-1980 of seawater were created for the study of water masses of ocean origin under the assumption of constancy of the salt composition. This made it possible to uniquely reproduce the scale of practical salinity and the associated scale of relative electrical conductivity, and to increase the accuracy of the equation of state depending on the variability of temperature and pressure in comparison with the equation of state of Knudsen, sørensen, Forch and Ekman.

     However, neither SHPS-1978 nor US-1980 solved the problem of indirect measurements of absolute salinity and density of sea water associated with the variability of salt composition (interionic ratios). If the spatial and temporal variation of the salt composition of ocean waters does not lead to an error in the indirect measurement of absolute salinity using SHPS-1978 more than DSA <=0.06 (see, for example, [1]), the difference in the salt composition of the marginal, Mediterranean or inland seas from the ocean makes it practically unacceptable to use SHPS-1978 and US-1980 in these waters. The joint group of experts on Oceanographic tables and standards (JGOTS), creating the SHPS-1978 and US-1980 for ocean waters, explicitly stated [ 2] that the development of regional scales of practical salinity and equations of state should be engaged in those States that are located in the coastal part of waters with a different salt composition from the ocean.

      Russia, Ukraine, Azerbaijan, Kazakhstan, and Georgia as former republics of the unified state of the USSR were engaged in research of the marginal seas of the Arctic and Pacific oceans, as well as the Mediterranean (Black, Azov, Baltic) and internal (Caspian, Aral) seas. Most of these studies were conducted the State Oceanographic Institute (SOI) of goskomgidromet with its offices, all-Union scientific research Institute of fisheries and Oceanography (VNIRO) of the USSR Ministry of fishery, Marine hydrophysical Institute (MHI NASU), Institute of Oceanology (IO RAS), Institute of biology of the southern seas (Inbum national Academy of Sciences of Ukraine). In recent years, intensive work has been carried out to study the salt composition and its dynamics in the marginal, Mediterranean and inland seas, as well as to assess the applicability of SHPS-1978 and US-1980 for these basins in the goin roskomgidromet Drumeva L. B., Luchkov V. P., Skorokhod AI, Tsitsari – nyma.G. and others.

     The authors have achieved some success in studying the modern salt composition of these water basins, determined the boundaries of salinity ranges in which the relative constancy of interionic ratios is observed, found refined relationships between the sum of ions and chlorine content, estimated the values of corrections or gave a new expression linking salinity with the relative electrical conductivity of desalinated waters in the range of unsteady and steady salt composition, and made the first steps to develop regional equations of state.

     However, given certain financial difficulties in the face of a shortage of necessary precision equipment and reagents, it would be desirable to pre-evaluate the most General, necessary and sufficient conditions for achieving the goals at possible financial costs. Egos primarily relate to such problems as the nature and stability of the relationship between the density of metamorphic waters with salinity and salinity, practical salinity scales of different periods and their relationship with each other and with absolute salinity, permissible error limits of scales and equations of state, as well as some questions of the methodology for performing certain technological operations in the development and reproduction of regional practical salinity scales (RSCPS) and equations of state (RUS). In this paper, an attempt is made to assess a priori some of the requirements for certain provisions in solving the above problems.

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