A global algorithm for estimating Absolute Salinity

[摘要] The International Thermodynamic Equation of Seawater – 2010 has defined thethermodynamic properties of seawater in terms of a new salinity variable,Absolute Salinity, which takes into account the spatial variation of thecomposition of seawater. Absolute Salinity more accurately reflects theeffects of the dissolved material in seawater on the thermodynamicproperties (particularly density) than does Practical Salinity.

When a seawater sample has standard composition (i.e. the ratios of theconstituents of sea salt are the same as those of surface water of the NorthAtlantic), Practical Salinity can be used to accurately evaluate thethermodynamic properties of seawater. When seawater is not of standardcomposition, Practical Salinity alone is not sufficient and the AbsoluteSalinity Anomaly needs to be estimated; this anomaly is as large as 0.025 g kg⁻¹ in the northernmost North Pacific. Here we provide an algorithmfor estimating Absolute Salinity Anomaly for any location (x, y, p) in the worldocean.

To develop this algorithm, we used the Absolute Salinity Anomaly that is foundby comparing the density calculated from Practical Salinity to the densitymeasured in the laboratory. These estimates of Absolute Salinity Anomalyhowever are limited to the number of available observations (namely 811). Inorder to provide a practical method that can be used at any location in theworld ocean, we take advantage of approximate relationships between AbsoluteSalinity Anomaly and silicate concentrations (which are available globally).

[学科分类] 海洋学与技术