TEOS-10 Software: Use It Or Lose It - 2

Fig. 1 Views Abound

I. Background

The first post in this series (here) about 3.5 years ago urged oceanographers to use official oceanographic software.

Dredd Blog has posted calculated thermal expansion information as well as thermal contraction information concerning ocean waters for a long time, using software from oceanography's official "Thermodynamic Equation of Seawater" (TEOS-10) site.

In other words, "practicing what we preach".

The following is helpful for understanding TEOS -10 (What every oceanographer needs to know about TEOS-10).

In that PDF file it is pointed out that "It is NOT RECOMMENDED that you try to programme these yourself. Instead, you should use software developed by members of SCOR/IAPSO WG127" (TEOS-10 Software).

Specifically, what has been done here on Dredd Blog is to use mostly the C++ version mentioned by Wikipedia ("TEOS-10 includes the Gibbs Seawater (GSW) Oceanographic Toolbox which is available as open source software in MATLAB, Fortran, Python, C, C++, R, Julia and PHP").

II.  The Nitty-Gritty of Thermal Expansion/Contraction Science

The old saying "what goes up must come down" applies to seawater temperatures in the sense that there are multiple depths in the ocean, which said depths are not at the same temperatures all the time.

Adding the laws of thermodynamics to that reality, and that deeper waters tend to be cooler than shallower waters in most cases, thermal contraction becomes an issue.

That is because the heat in warmer seawater flows to any colder seawater around it (Second Law of Thermodynamics).

The seawater that once had the heat that flowed to colder water will then contract back to the temperature level and density that it was at before that heat flowed out to the seawater around it (that was warmed up and expanded to a new level itself).

This takes place at the atom/molecule level, not at the "ocean current" level);

How fast or slow this takes place varies with the composition of the seawater involved.

In situ (actual) measurements Dredd Blog uses are featured in the World Ocean Database. 

Those measurements include up to thirty-three depth levels in all of the relevant world oceans which have been contributed by seafarers for over a century.

III. Application of 'The Second Law' Using TEOS-10

Here is a quote from a Dredd Blog post that focuses on this not-well-enough-understood (or just plain ignored) subject:

"... Improper/Proper Techniques

One paper I noticed explains a fundamental basis for the proper techniques and procedures involved in proper thermal expansion and contraction analysis of seawater:

"A common practice in sea level research is to analyze separately the variability of the steric and mass components of sea level. However, there are conceptual and practical issues that have sometimes been misinterpreted, leading to erroneous and contradictory conclusions on regional sea level variability. The crucial point to be noted is that the steric component does not account for volume changes but does for volume changes per mass unit (i.e., density changes). This indicates that the steric component only represents actual volume changes when the mass of the considered water body remains constant."

(On the interpretation of the steric and mass components of sea level variability, VOL. 118, 953–963, doi:10.1002/jgrc.20060, by Gabriel Jordà and Damià Gomis, 2013; @p. 953, 954, emphasis added). In other words the mass quantity must be considered constant as the seawater temperature changes.

I use the World Ocean Database (WOD) data segmented into thirty three depth levels at several hundred WOD Zones.

Since the WOD Zone boundaries are latitude and longitude determined, and since the Earth is a globe, each WOD Zone's volume and mass varies from zone to zone  because the four 'sides' of the zone are different lengths and the ocean depths vary (the zone boundaries appear to be even on the WOD map for easier selection).

But more than that, each separate depth level (L1 - L33) and pelagic group varies (see Section IV below). 

So, to comply with the proper way of determining thermal expansion and contraction, one must determine the mass/density of each of the thirty-three depth level segments and calculate them individually.

The next most important factor is called the "Thermal Expansion Coefficient" (TEC) that I calculate using the TEOS-10 function gsw_alpha in the C++ software version:

% gsw_alpha: thermal expansion coefficient with respect to
% Conservative Temperature (75-term equation)
%
% USAGE:
% gsw_alpha(SA,CT,p)
%
% DESCRIPTION:
% Calculates the thermal expansion coefficient of seawater with respect to
% Conservative Temperature using the computationally-efficient expression
% for specific volume in terms of SA, CT and p (Roquet et al., 2015).
%
% Note that this 75-term equation has been fitted in a restricted range of
% parameter space, and is most accurate inside the "oceanographic funnel"
% described in McDougall et al. (2003). The GSW library function
% "gsw_infunnel (SA,CT,p)" is avaialble to be used if one wants to test if
% some of one's data lies outside this "funnel".
%
% INPUT:
% SA = Absolute Salinity [g/kg]
% CT = Conservative Temperature (ITS-90) [deg C]
% p = sea pressure [dbar]
%( i.e. absolute pressure - 10.1325 dbar)
%
% OUTPUT:
% alpha = thermal expansion coefficient [1/K]
% with respect to Conservative Temperature
%
% AUTHOR:
% Paul Barker and Trevor McDougall[ help@teos-10.org ]
%
% VERSION NUMBER: 3.06.12 (25th May, 2020)
%
% REFERENCES:
% IOC, SCOR and IAPSO, 2010: The international thermodynamic equation of
% seawater - 2010: Calculation and use of thermodynamic properties.
% Intergovernmental Oceanographic Commission, Manuals & Guides # 56,
% UNESCO (English), 196 pp. Available from http://www.TEOS-10.org
% See Eqn. (2.18.3) of this TEOS-10 manual.
%
% McDougall, T.J., D.R. Jackett, D.G. Wright and R. Feistel, 2003:
% Accurate and computationally efficient algorithms for potential
% temperature and density of seawater. J. Atmosph. Ocean. Tech., 20,
% pp. 730-741.
%
% Roquet, F., G. Madec, T.J. McDougall, P.M. Barker, 2015: Accurate
% polynomial expressions for the density and specifc volume of seawater
% using the TEOS-10 standard. Ocean Modelling., 90, pp. 29-43.
%
% The software is available from http://www.TEOS-10.org
%
%
double TeosBase::gsw_alpha(double sa, double ct, double p)
{

/** for GSW_TEOS10_CONSTANTS use gtc */
double xs, ys, z, v_ct_part;

xs = sqrt(gtc.gsw_sfac*sa + gtc.offset);
ys = ct*0.025;
z = p*gtc.rec_db2pa;
v_ct_part = gsw_get_v_ct_part(xs, ys, z);

return 0.025*v_ct_part/gsw_specvol(sa,ct,p);

}

(gsw_alpha in the C++ version of source code library). I don't know if this function is available in the other software versions.

Finally, all of the above procedures (Section II) must be done in a proper sequence as follows:

1) use the same exact data used to calculate potential enthalpy used in Dredd Blog post The Photon Current - 10.

2) use the same exact TEOS-10 functions that were used in that post to generate Conservative Temperature (CT), Absolute Salinity (SA), and pressure (P). 

3) then use the gsw_alpha function to generate the TEC; then this formula to generate the thermal expansion/contraction value:

V1 = V0 * (1.0 + (B * DT))

where:

V0 = mass_unit_vol

DT = D - T

D = current temperature
B = thermal expansion/contraction coefficient (TEC);
T = previous temperature
V1 = thermal expansion/contraction (volume change)

 

Sorry if I have oversimplified this discussion."

(On Thermal Expansion & Thermal Contraction - 49). The subject matter is important enough that the issue should be studied even though it may raise a sweat on the intellectual brow of a researcher.

IV. They're Not Back Still ("Crickets")

Papers written since that Dredd Blog series began have not picked up on this fundamental way of determining the real thermal expansion/contraction values taking place in the recorded past, and taking place now.

Thus, these scientific journal papers give conflicting and incorrect values.

Furthermore, since they conclude that thermal expansion is the major, or a major cause of sea level rise, they miss the fact that tidewater glacier melting is the primary cause by a significantly larger margin (Hot, Warm, & Cold Thermal Facts: Tidewater-Glaciers - 9).

The previous post in this series is here.

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It's Been A Long Time Coming

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