Estimating Absolute Salinity (SA) in the World's Oceans Using Density and Composition

Abstract:

The practical salinity (S_p), which is determined by the relationship of conductivity to the known proportions of the major components of seawater, and reference salinity (S_R = (35.16504/35)*S_p), do not account for variations in physical properties such as density and enthalpy. Trace and minor components of seawater, such as nutrients or inorganic carbon and total alkalinity affect these properties and contribute to the absolute salinity (S_A). This limitation has been recognized and several studies have been made to estimate the effect of these compositional changes on the conductivity-density relationship. These studies have been limited in number and geographic scope. Here, we combine the measurements of previous studies with new measurements for a total of 2,857 conductivity-density measurements covering all of the world’s major oceans to derive empirical equations for the effect of silica and total alkalinity on the density and absolute salinity of the global oceans and recommend an equation applicable to most of the world oceans. The potential impact on salinity as a result of uptake of anthropogenic CO₂ is also discussed.