Sigma-t

Sigma-t is a quantity used in oceanography to measure the density of seawater at a given temperature.^[1] σ_T is defined as ρ(S,T)-1000 kg m⁻³, where ρ(S,T) is the density of a sample of seawater at temperature T and salinity S, measured in kg m⁻³, at standard atmospheric pressure. For example, a water sample with a density of 1.027 g/cm³ has a σ_T value of 27.