Potential density

The potential density σ _θ
plotted against the salt content in the water

The potential density is the density of sea ​​water under normal conditions compared to the density of pure water . It is a state variable and enables a comparison of water masses . ${\displaystyle \sigma _{\Theta }}$

Definition and basics

In oceanography , the density of water is an important parameter, as horizontal density differences lead to currents . Analogously to the potential temperature , the potential density is introduced, which indicates the density at normal pressure and as a deviation from the true density of water (1000 kg / m ³ ):

${\displaystyle \sigma _{\Theta }=\rho \left(S,\Theta \right)-1000\,{\frac {\mathrm {kg} }{\mathrm {m} ^{3}}}}$

With

• ${\displaystyle \rho }$: Density at normal pressure (1013 mbar), depending on
  • the salinity and ${\displaystyle S}$
  • the potential temperature . ${\displaystyle \Theta }$

See also

• relativ density