Dredd Blog: On Thermal Expansion & Thermal Contraction

Fig. 1a

Thermal expansion of pure water does not have the same thermodynamic events that the thermal expansion of sea water has.

Nevertheless, you can search the Internet and find videos of someone pouring pure water into a flask, making a mark on the flask, then heating the flask with a Bunsen Burner.

Then, after the water warms, they will put another mark on the flask ostensibly showing that the heat has caused the water to increase in volume.

Then they are apt to declare that this proves that thermal expansion is the major cause of sea level rise because "as water warms it expands."

The problem with this Mickey Mouse trick is that the pure water they use is at a temperature that is not below its maximum density temperature of 4 deg. C when they apply heat to the flask.

If it was, the pure water would contract (lose volume) rather than expand (gain volume) until the pure water temperature reached the maximum density temperature of 4 deg C.

From that temperature on, it would begin to expand as more heat is applied (see Fig. 1a).

Fig. 1b

For example, if the pure water temperature is 2 degrees C and heat is applied, the water will contract (lose volume) until its temperature increases to the maximum density temperature of 4 deg C, at which point it will expand (gain volume) if more heat is added.

Determining the maximum density of sea water is more difficult than with pure water, because sea water contains other substances, and also is impacted by depth pressure (Is A New Age Of Pressure Upon Us? - 14).

Fig. 1c

The graphs at Fig. 1b and Fig. 1c show a history of the sea water temperature in a Hypotherical WOD Zone at 10-20 meters deep (see actual graphs here).

Following the principles depicted in Fig. 1a, I have marked the expansion and contraction events to show the almost unbelievable expanding and contracting actions as the sea water temperature (black line) dips below or rises above the maximum density temperature (maximum density temperature is shown by the red line).

The gist of it is that when the sea water temperature (black line) is above the maximum density temperature (red line) the volume change is the opposite of what it is when the sea water temperature (black line) is below the maximum density temperature (red line).

The non-marked-up version of the Fig. 1b graph is shown at Fig. 1c.

Today, I used only one zone, specifically for emphasizing that the net balance derived by adding up the thermal expansion (pluses), and subtracting the thermal contractions (minuses) does not result in either "the major factor" or "a major factor" of sea level rise.

The graph at Fig. 1c, as well as the following graphs, were computed by using the TEOS-10 function gsw_ct_maxdensity to create the red line, and gsw_ct_from_t to generate the black line (see On Thermal Expansion & Thermal Contraction - 35).

Each of the following graphs (Fig. 2a - Fig. 2r) was generated using data from a different depth, but they are all constructed from WOD data collected in WOD Zone 5611.

TEST: see if you can determine expansion and contraction segments of the black line as I did in Fig. 1b. [Remember to follow the time line flow (left to right): Answers]

Remember that (in terms of whether expansion or contraction will take place) when the black line is above the red line, sea water thermodynamics are the opposite from when the black line is below the red line (cf On Thermal Expansion & Thermal Contraction - 35).

This is why we need this focus:

"The vast Southern Ocean, which surrounds Antarctica, plays a starring role in the future of climate change. The global oceans together absorb over 90 percent of the excess heat in the climate system and roughly three-quarters of that heat uptake occurs in the Southern Ocean. In addition, the global oceans absorb around 25 percent of anthropogenic carbon dioxide emissions and the Southern Ocean alone accounts for about half of the uptake of CO2.

Despite its critical role in our climate system, the Southern Ocean has gone almost completely unobserved. Scientists have struggled to gather precise measurements because of the harsh environment and extreme remoteness. The changing dynamics of the Southern Ocean will in turn drive key aspects of our future climate, including how sensitive the Earth will be to further warming and increases in carbon dioxide emissions. As a result, improved observations are crucial to helping scientists understand and predict how our climate will change."

(Antarctica 2.0 - 3, quoting Climate Central). When the sea level is rising and the net result of thermal expansion / contraction totals is a minor player, a small number, then melting tidewater glaciers and other melting ice in the Cryosphere quite obviously must be the major player.

Finally, yes the lines on the graphs are somewhat jerky because that area of the world makes it difficult to take measurements.

There are not as many measurements over the decades as we would like (especially at deepest depths), but there are enough to give us a heads up.

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