ODM2 Variable Name Controlled Vocabulary ODM2 Working Group A vocabulary for describing the name of Variables. Sigma-t Density of seawater calculated with in situ salinity and temperature, but pressure equal to zero, rather than the in situ pressure, and 1000 kg/m^3 is subtracted. Defined as (S,T)-1000 kg m-3, where (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. Originally from the CUAHSI HIS VariableNameCV. See: http://his.cuahsi.org/mastercvreg/edit_cv11.aspx?tbl=VariableNameCV.