|Fig. 1 The Real Picture|
The specific half-truth is that "water expands when heat is added to it" (ibid).
The graphic at Fig. 1 shows that both the maximum and minimum density of water depends on its temperature, which is 4 deg. C for fresh water, but lower for seawater.
If this issue wasn't such a critical issue to current civilization I would not be writing Dredd Blog posts about it (see e.g. The Extinction of Robust Sea Ports, 2, 3, 4, 5, 6, 7, 8, 9).
That half-truth is the foundation for the hypothesis that "thermal expansion is the major or a major cause of global sea level rise" (On Thermal Expansion & Thermal Contraction, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40).
I have noticed that, in the warming science commentariat literature, the percentage alleged in the hypothesis has been coming down from "most", to "half", to "a third", and recently "a fourth".
|Fig. 2 WOD Layers|
If the direct warming of the oceans by sunlight was the major cause of sea level rise (SLR) and sea level fall (SLF), one would think that the percentage would be going up as the average global atmospheric temperature increases from year to year.
If the ocean heat content is causing the percentage of thermal expansion to decrease, then the ocean heat content must be decreasing too (see On Thermal Expansion & Thermal Contraction - 40).
The reality is that OHC is constantly increasing and thermal expansion never was "the" or even "a" major cause of SLR or SLF.
Sea level change (SLC), whether in the form of SLR or SLF, has always been caused by, and still is caused by, the disintegration of ice sheets (Antarctica, Greenland) and land based glaciers (world wide locations).
|Fig. 3a Layer 1 (Panels)|
|Fig. 3b Layer 1 (Lines)|
|Fig. 3c Layer 1 (expansion,contraction)|
|Fig. 4a Layer 2 (Panels)|
|Fig. 4b Layer 2 (Lines)|
|Fig. 4c Layer 2 (expansion,contraction)|
The graphs at Fig. 3a - Fig. 3c show that at times the maximum density temperature in WOD Layer 1 can be higher (warmer) than the actual seawater temperature there.
Which means that if you add heat to that seawater it will not expand, it will contract (thermal contraction).
The graphs at Fig. 4a - Fig. 4c show the same scheme for WOD Layer 2.
The red line on Fig. 3b and Fig. 3c indicates the maximum density temperature.
The maximum density temperature is the temperature where the seawater cannot be compressed further (it can only expand at that temperature).
The black lines on the graphs at Fig. 3b and Fig. 3c indicate the measured (in situ) temperature converted into Conservative Temperature (CT) by the TEOS-10 software (TEOS-10).
The small squares on Fig. 3c indicate whether the change in temperature (CT) causes thermal expansion or thermal contraction.
Since the CT line (black line) is below the maximum density line (red line) any addition of heat (temperature increase) causes thermal contraction while removal of heat (temperature decrease) causes thermal expansion.
The long and short of it is that, like the graphic at Fig. 1 shows, the temperature of the seawater at the time heat is added or removed determines whether thermal expansion or contraction will result.
The graphs at Fig. 4b and Fig. 4c are depictions of WOD Layer 2.
The same thermodynamic principles apply in Layer 1 and Layer 2.
Anytime a heat content change causes the temperature line to move toward the maximum density line thermal contraction is taking place and anytime the temperature line is moving away from the maximum density line thermal expansion is taking place.
The other graphs at Fig. 3a (Layer 1) and Fig. 4a (Layer 2) have four individual panels.
The upper left panels show Conservative Temperature (CT) while the lower left panels show Potential Enthalpy (hO).
The CT and hO have the same pattern because they are in thermodynamic proportion (Patterns: Conservative Temperature & Potential Enthalpy - 2).
The upper right and lower right panels on Fig. 3a and Fig. 4a depict a different type of proportion.
The upper right Maximum Density and the lower right Absolute Salinity are opposites in proportion in the sense that when one goes up the other goes down.
The previous post in this series is here.