Dichte von Meerwasser/Seawater density

Ich war gerade mal neugierig, wie die Dichte des Meerwassers von Salzgehalt und Temperatur abhängt, und habe das folgende zusammengesucht. Die Salzwasser-Korrektur bezieht sich auf eine andere (von mir nicht auffindbare) Süßwasserdichte als die hier verwendete, sodass das Ergebnis eventuell ungenau ist. Für den Salzgehalt gibt es verschiedene Standards ("Reference Salinity", "Practical Salinity", "Conductive Salinity", "Chlorinity" - mit den Details habe ich mich nicht beschafft, einiges steht bei Millero/Huang), grob gesagt ist es einfach die Angabe in Massepromille.

I was curious about the density of seawater depending on temperature and salinity, and found the following stuff. The salinity corrections in the cited paper use some other freshwater density equation than the one given here (the only one for which I found a paper), so the results might be somewhat inprecise. The salinity can be defined by different standards ("Reference Salinity", "Practical Salinity", "Conductive Salinity", "Chlorinity" - I did not study the details), some information is in the paper by Millero/Huang.
Essentially it is the salt content in mass promille.

Gnuplot source:

# start
# density in kg/m^3, Temp. in Celsius
# Salinity in mass promille
rho0(t)=r5*(1.0-((t+r1)**2*(t+r2))/(r3*(t+r4)))
# freshwater density: Tanaka et al., cited in
# Becerra: "Water density"
#02%20Water%20density%20and%20its%20uncertainty_Luis%20O%20Becerra.pdf
r1=-3.983035
r2=301.797
r3=522528.9
r4=69.34881
r5=999.97495
# Salinity correction
# Millero+Huang, "The density of saltwater as a function ...",
# Ocean Sci. 5, 91-100, 2009
# http://www.ocean-sci.net/5/91/2009/os-5-91-2009.html
rho(t,s)=rho0(t)+s*(A(t)+sqrt(s)*B(t)+s*C(t))
A(t)=a0+t*(a1+t*(a2+t*(a3+t*(a4+t*a5))))
B(t)=b0+t*(b1+t*b2)
C(t)=c0
# 0≤t≤40, other ranges see table 2. in Millero/Hunag
a0=8.246111e-1
a1=-3.956103e-3
a2=7.274549e-5
a3=-8.239634e-7
a4=5.332909e-9
a5=0
b0=-6.006733e-3
b1=7.970908e-5
b2=-1.018797e-6
c0=5.281399e-4
# end

Ergebnisse/Results (click on pictures to embiggen)

Fig. 1: Density. The effect of the salinity dominates, the anomaly is invisible

Fig 2: Flattened picture obtained by plotting ρ-0.8*s, making the anomaly visible. The contour plot on the floor clearly indicates how the anomaly vanishes for salinities over ≈ 20 (i.e. 2 mass-%)