Ocean Science
www.ocean-sci.net
1812-0784
1812-0792
5
2
2009
10.5194/os-5-91-2009
http://www.ocean-sci.net/5/91/2009/
http://www.ocean-sci.net/5/91/2009/os-5-91-2009.html
http://www.ocean-sci.net/5/91/2009/os-5-91-2009.pdf
91
100
2009-05-05
The density of seawater as a function of salinity (5 to 70 g kg<sup>−1</sup>) and temperature (273.15 to 363.15 K)
F. J. Millero
fmillero@rsmas.miami.edu
F. Huang
Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, FL 33149, USA
New seawater density measurements were made as a function of temperature <i>T</i>=(273.15 to 363.15) K and salinity (5 to 70 g kg<sup>−1</sup>).
The measurements (<i>N</i>=230) from <i>T</i>=273.15 to 313.15 K and Practical Salinity (<i>S</i>) from 0 to 40
were found to be in good agreement (σ=0.0036 kg m<sup>−3</sup>) with the
equation of state of seawater (Millero and Poisson, 1981) made on samples
with a known chlorinity (Cl). These results indicate that the Practical
Salinities (<i>S</i>) are in agreement to within ±0.003 kg m<sup>−3</sup> with the
values calculated from the Chlorinity, <i>S</i><sub>Cl</sub>=1.80655 Cl. The
measurements from 298.15 to 363.15 were used to extend the equation of state
to high temperatures and salinities. All the densities were made relative to
pure water (ρ−ρ<sup>0</sup> where ρ<sup>0</sup> is the density for
pure water) were fitted to equations of the form
<br><br>
(ρ−ρ<sup>0</sup>)/(kg m<sup>−3</sup>)=<i>A S<sub>A</sub>+B S<sub>A</sub><sup>1.5</sup>+C S<sub>A</sub><sup>2</sup></i>
<br><br>
where <i>A</i>, <i>B</i>, and <i>C</i> are functions of temperature and <i>S<sub>A</sub></i> (g kg<sup>−1</sup>) is
the absolute salinity, <i>S<sub>A</sub></i>=(35.16504/35) <i>S</i> g kg<sup>−1</sup>. The fitted
results from <i>S<sub>A</sub></i>=0 to 50 g kg<sup>−1</sup> and <i>T</i>=273.15 to 313.15 K (<i>N</i>=242) gave standard errors of 0.0037 kg m<sup>−3</sup>. The fitted results from
298.15 to 363.15 K (<i>N</i>=280) gave standard errors of 0.0063 kg m<sup>−3</sup> and
all the results (<i>N</i>=522) from 273.15 to 363.15 K gave standard errors of
0.0063 kg m<sup>−3</sup>. The earlier density measurements (Millero et al., 1976b;
Poisson et al.,1980) used to determine the equation of state of seawater
(Millero and Poisson, 1981) were combined to derive equations that are valid
from 273.15 to 313.15 K and 273.15 to 363.15 K. The standard errors of these
fits are respectively, 0.0038 kg m<sup>−3</sup> (<i>N</i>=713) and 0.0063 kg m<sup>−3</sup>
(<i>N</i>=962). These new measurements expand the equation of state of seawater
to a wider range of temperature (273.15 to 363.15) K and absolute salinity
(0 to 70 kg m<sup>−3</sup>.
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