Let's Not Be Too Dense

Fig. 1 Density Matters

In a recent Dredd Blog post I quoted the World Ocean Database (WOD) Manual, and pointed out a very interesting quote in it:

The reason I have ventured into the sea water density issue is because of what is written in the TEOS-10 manual:

"Since the density of seawater is rarely measured, we recommend the approach illustrated in Figure 1 as a practical method to include the effects of composition anomalies on estimates of Absolute Salinity and density. When composition anomalies are not known, the algorithm of McDougall et al. (2012) may be used to estimate Absolute Salinity in terms of Practical Salinity and the spatial location of the measurement in the world oceans."

(TEOS-10 Manual, p. 14, p. 24 PDF).

(On Thermal Expansion & Thermal Contraction - 35, emphasis added). That could be quite significant.

As the graphic at Fig. 1 shows, the maximum density temperature of the sea water is an important part of determining whether contraction or expansion will take place as the temperature of the sea water being analyzed changes.

Unless one calculates the density and the maximum density temperature, one can not know whether thermal contraction or thermal expansion is taking place at any given in situ context.

In other words one will not have a clue as to how much or even whether or not sea level is being impacted by the change in sea water temperature.


Furthermore, the density is quite easy to determine, and so is the maximum density temperature, when one is using the TEOS-10 software library to analyze in situ measurements.

Fig. 2See Fig. 2m here

While writing software modules and using actual in situ sea water temperature measurements around Antarctica, then generating graphs, I noticed that at times the Conservative Temperature and the Maximum Density Conservative Temperature run parallel to one another.

"Does thermal contraction or expansion take place when they run parallel to one another?" I wondered.


The graph at Fig. 2 is an example showing several years where the sea water temperature and the maximum density temperature ran parallel.

The initial data indicates that even though the sea water temperature (Conservative Temperature - CT) was increasing quite a bit the thermosteric volume was not.

I will finish those modules soon, and share the results.

Hopefully we can determine if and how much this impacts the thermal expansion hypothesis.

The hypothesis I am talking about is the one that alleges that thermal expansion is the main cause of sea level rise.

Stay tuned.