The World According To Measurements - 7

Fig. 1 Climate Central

Since the Thermodynamic Equation Of Seawater - 2010 (TEOS-10) became available some have wondered about it.

The freely available toolkit comes in several programming languages and can be easily downloaded (TEOS-10 Software).

As to relevant changes brought about by TEOS-10, nothing has changed with regard to taking measurements, a point that the scientists involved emphasize:

"Importantly, while Absolute Salinity (g/kg) is the salinity variable that is needed in order to calculate density and other seawater properties, the

Fig. 2 Sea level change measurements

salinity which should be archived in national data bases continues to be the measured salinity variable, Practical Salinity (PSS-78). To avoid confusion while the use of Practical Salinity in scientific publications is phased out, published values of salinity should be specifically identified as being either Practical Salinity with the symbol S_P or Absolute Salinity with the symbol S_A."

(TEOS). In other words, keep on measuring in situ, but analyze those measurements with the new techniques that will result in more accurate and coherent discussions.

The heat being stored in the oceans takes exacting measurements and processes in order to track and study it:

"Roemmich estimates that at depths from 500 to 2000 meters, oceans are warming by .002 degrees Celsius every year, and in the top 500 meters, they’re gaining .005 degrees C. annually. While that may not seem like a

Fig. 3 Sea level impacts compared

big temperature jump, it amounts to a staggering load of heat when multiplied throughout the depths of this immense system that covers 70 percent of the planet.

Temperature gains are larger at the sea surface, which heats faster than the ocean as a whole. The top 75 meters have warmed an average of .01 degrees C per year since 1971."

(Yale, cf Fig. 1). The ".002" and ".005" values are tiny because the ocean is so voluminous that it can take a truly vast amount of heat, but it can also distribute that heat widely enough that detecting it in the deeps is a science in itself.

Fig. 4 Practical and Absolute Salinity

That said, I prepared some graphs to show how I distinguish between the "practical salinity" (measured in the ocean "in situ") and "absolute salinity" so as to keep the two concepts clean.

As the TEOS site suggested ("the salinity which should be archived in national data bases continues to be the measured salinity variable") I store the in situ data that I download from the World Ocean Database (WOD) in an SQL database in the original values (except the ~1% that are out of bounds, as noted here).

Fig. 5 Conservative and In Situ Temperatures

I like to be transparent so I prepared some graphs using a software module that processes both S_A ("Absolute Salinity") and S_P ("Practical Salinity" or in situ or measured salinity) separately.

The graph at Fig. 4 compares Absolute Salinity with Practical Salinity, and the graph at  Fig. 5 compares the TEOS-10 concept "Conservative Temperature" with the in situ or in place measurements stored in the WOD database.

Fig. 6 Volume Change Comparison

I even did a graph that compares thermosteric volume change using Absolute Salinity and Conservative Temperature (TEOS concepts) with thermosteric volume change using measured temperature and salinity (Fig. 6).

These graphs use different colors for each type, and use a granularity that makes it easier to see the differences than panel graphs do (Fig. 3).

That said, it is still obvious that the relevant "thermal" condition is not expansion (it is contraction) no matter which type of graph is used for comparison.

The next post in this series is here, the previous post in this series is here.

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