An algorithm for estimating Absolute Salinity in the global ocean

Abstract

To date, density and other thermodynamic properties of seawater have been calculated from Practical Salinity, SP. It is more accurate however to use Absolute Salinity, SA (the mass fraction of dissolved material in seawater). Absolute Salinity SA can be expressed 5 in terms of Practical Salinity SP as SA=(35.165 04g kg−1/35)SP + δSA(ϕ, λ,p) where δSA is the Absolute Salinity Anomaly as a function of longitude ϕ, latitude λ and pressure. When a seawater sample has standard composition (i.e. the ratios of the constituents of sea salt are the same as those of surface water of the North Atlantic), 10 the Absolute Salinity Anomaly is zero. When seawater is not of standard composi- tion, the Absolute Salinity Anomaly needs to be estimated; this anomaly is as large as 0.025g kg−1 in the northernmost North Pacific. Here we provide an algorithm for estimating Absolute Salinity Anomaly for any location (ϕ, λ,p) in the world ocean. To