On the deuterium-salinity relationship in the Baltic Sea

Two vertical deuterium profiles at the Bornholm Basin in the Baltic Sea are described. Both profiles show a uniform deuterium content from the surface down to about 40 m. At greater depths the deuterium content increases. Supplemented by measurements of Friedman (1964) the usual linear relationship between deuterium content and salinity is established. This linear relationship is also derived theoretically from the consideration of a box model and the resulting balance equations for water, salinity and isotopes in the upper layer. Comparison of the experimental and theoretical deuterium-salinity relationship yields ratios of hydrographic parameters such as the ratio of annual evaporation to fresh water inflow, which in the case of the Baltic Sea can be checked with the known value.