sigma-t density (σ-t density) The density of a sea-water sample measured at atmospheric pressure, i.e. at the sea surface. It is defined as density minus 1000, where the density is measured in kg/m³. Thus sea water at 0°C and 35 parts per thousand salinity has a density of 1028 kg/m³, or a σ-t density, at a pressure of 1 bar, of 28.

sigma-t density(σ-t density) The density of a sea-water sample measured at atmospheric pressure (i.e. at the sea surface). It is defined as density minus 1000, where the density is measured in kg/m³. Sea water at 0°C and 35 parts per thousand salinity has a density of 1028 kg/m³, or a σ-t density, at a pressure of 1 bar, of 28.