Sunday, October 21, 2018

On Thermal Expansion & Thermal Contraction - 39

Fig. 1 Water terminating glacier
I. Foreward

Non-intuitive situations in scientific research can cause communication problems (e.g. The Gravity of Sea Level Change) .

One example is when one is trying to communicate the answer to the question: "Why does the TEOS-10 function gsw_enthalpy_t_exact indicate that there is more "heat" in deep ocean water than there is in shallow ocean water, even when they are both at the same temperature?"

II. The Area of Concern

I modified a graphic (Fig. 1) of a tidewater glacier terminus in order to focus on the ocean depth at which the subsurface "face" of such glaciers begin and end.
Fig. 2 W. Indian Ocean

In this case the "face" is the glacial ice from the top of the glacier to the glacier's grounding line below sea level.

For example, the face of Totten Glacier in Antarctica (WOD Zone 3611) reaches 2,500 meters below sea level (from grounding line up to sea level is ~2500m).

Fig. 3 E. Indian Ocean
With less of a face, Thwaites Glacier in Antarctica (WOD Zone 5710) is nicknamed "the Doomsday Glacier".

I am providing graphs of the Antarctic areas of those two zones.

They are graphs that detail the specific enthalpy of those areas.

Today's graph that features Thwaites Glacier's specific enthalpy is at Fig. 6, and the graph that features Totten Glacier's specific enthalpy is at Fig. 3.

There are many other glaciers in those graphed areas.

I am mentioning Thwaites and Totten because they represent enough sea level rise to destroy our current global sea-trade-based civilization (The Extinction of Robust Sea Ports - 10).

III. Enthalpy or Specific Enthalpy? 

These entities (enthalpy and specific enthalpy) are described in various and sundry ways:
Simple English view

A chemistry view

The definition of enthalpy Encyclopedia Britannica.

Enthalpy reflects "the capacity to release heat." (Quora).
But, since I use the TEOS-10 toolkit for my seawater thermodynamic computations, that is where I focus my efforts.

One of the TEOS-10 documents states: "The specific enthalpy is therefore a measure of the heat content of the system" (TEOS-10 Primer, p. 8, emphasis added).

That there is "specific enthalpy" as well as "enthalpy" necessitates some clarification:
Fig. 4 Ross Sea
"[formula for enthalpy:] "H = U + pV, where H is the enthalpy of the system, U is the internal energy of the system, p is the pressure of the system, V is the volume of the system.
...
[formula for specific enthalpy:] h = u + pv, where u is the specific internal energy, p is the pressure, and v is specific volume."
(Wikipedia, emphasis added). Ok, but are capital letters vs lower case letters the only difference?

Either way, since "p is the pressure", it is easy to see that both enthalpy and specific enthalpy tend to encapsulate a quantity increase (J / kg) as the ocean depth (and therefore pressure) increases.

But, is that the gravamen, the essential matter of the situation?

No, because once again "mass unit" comes to the forefront:
"A common practice in sea level research is to analyze separately the variability
Fig. 5 Amundsen Sea
 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 Thermal Expansion & Thermal Contraction - 38). And this factor dovetails quite well with the "specific enthalpy" vs "enthalpy" consideration:
"Specific Enthalpy is the total energy in a system due to pressure and temperature per unit of mass in that system. Specific enthalpy is used in thermodynamic equations when one wants to know the energy for a given single unit mass of a substance. The SI units for specific enthalpy are kJ/kg (kilojoules per kilogram).

Specific enthalpy is calculated by taking the total enthalpy of the system
Fig. 6 Bellingshausen Sea
and dividing it by the total mass of the system. It is written mathematically as:


h = H/m

where h is the specific enthalpy, H is the enthalpy of the system, and m is the total mass of the system. Specific enthalpy can also be written in terms of specific energy, pressure, and specific volume such that the following equation is true:

h = u + pv

where u is the specific energy, p is the pressure and v is the volume. This is to be seen as the specific enthalpy version of, and not to be confused with, the enthalpy equation:

H = U + pV

where H is the total enthalpy, U is the energy of the work done in the system, p is pressure, and V is the volume of the system."
(Calcularor Org). It is fundamental that the mass unit (in this case a zone bounded by latitude and longitude lines at various depth slices ... e.g. 10-20m) be identified and quantified prior to doing thermal expansion or specific enthalpy calculations.

IV. What About The Graphs?

As we peruse today's graphs, note that they not only concern the context of specific enthalpy, they also concern the context of thermosteric sea level change (a.k.a. thermal expansion / contraction).

Fig. 7 Weddell Sea
Notice that the graphs are the exact opposite of what is hypothesized in the "thermal expansion is the greatest cause of sea level rise in the 20th century" myth.

The deepest waters, way down far away from warming sunlight and the global warming induced greenhouse effect at the ocean's surface, is where specific enthalpy ("a measure of the heat content of the system") is strongest (Fig. 2 - Fig. 7).

In other words, all things being the same, the deeper water is where the "heat" is most abundant in terms of Joules per kilogram (J / kg).

V. Conclusion

The main cause of that non-intuitive factor is the pressure at deep depths, where the glacial ice face is most vulnerable to Antarctic current driven warming.

It takes just a little warming down there to cause a lot of melt water to flow upwards in a plume (Frontal processes on tidewater glaciers).

Other Conservative Temperature graphs indicate that, in places, those deep waters have warmed about a degree Celsius, like the Earth's atmosphere way above those waters has (GISS).

The previous post in this series is here.

Thursday, October 18, 2018

Hot, Warm, & Cold Thermal Facts: Tidewater-Glaciers - 6

Fig. 1a
Fig. 1b
Fig. 1c
This series points out why a great heatwave of hot water is not what is melting tidewater glaciers (Hot, Warm, & Cold Thermal Facts: Tidewater-Glaciers, 2, 3, 4, 5).

All that is required to melt tidewater glaciers is seawater that is less cold than those tidewater glaciers.

The speed of melt is what is impacted by the temperature difference between the subsurface glacier ice and the seawater in contact with it.

Generally, a one degree difference will cause a slower melt than a three degree difference.

But there are exceptions, such as amount of salinity or refreshing currents which bring in new seawater with more potency.

The importance of that can be discerned by graphics at Fig. 1a - Fig. 1c.

The story begins with a time line which depicts years of temperature variation between the seawater temperature and the temperature of the glacial ice in contact with the seawater (Fig. 1a).

Next is the contact with the ice face of the tidewater glacier (Fig. 1b).

That contact leads to the scenario in Fig. 1c, where a new entity, melt water (the green color between the cyan color and the blue color), appears on the scene.

The basic dynamic at work that causes the melting is a matter of energy transfer described by the Second Law of Thermodynamics:
Now that we have been brave enough to admit the existence of thermal contraction, we can consider the Second Law of Thermodynamics.

I mean that we can do so at least in the sense of the movement of heat in the oceans (which has one and only one direction) which is from warm to cold (NASA, Univ. of Winnipeg).
(On Thermal Expansion & Thermal Contraction - 26). The energy in the form of heat in the cold (but warmer than ice) water contacting the glacial ice flows spontaneously into the colder ice mass.

When enough energy has entered into the ice mass it causes the ice to exceed the temperature of ice, so it changes in structure to become melt water.

That melt water has more heat energy in it than the ice it came from had, but it has less heat energy than the warmer seawater had that originally contacted the ice.

That by itself (melt water is cooler than the seawater that caused it) would slow down the process if all things remained that way.

A perpetual melt water buffer would slow down the melt rate.

That is, because the melt water has less heat energy than the original water that made contact with the ice, the speed of the melting would slow down a bit.

But, the thing about Antarctica is that it's tide waters in contact with tidewater glaciers is substantial and is refreshed regularly:
"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 - 6). Antarctica has the world's greatest current in the sense that more water flows within that current that in all the rivers on Earth combined:
"The Antarctic Circumpolar Current moves 140 million cubic meters (4.9 billion cubic feet) of water per second around Antarctica. That single current moves more water than all the rivers on the planet combined. The world's rivers move 1.3 million cubic meters (46 million cubic feet) of water per second."
(Mysterious Zones of Antarctica - 2). Thus, the melt is not slowing down there, no, it is accelerating because the water in contact with tidewater glaciers is refreshed by a major current (which removes cooler melt water).

I have prepared graphs (like the symbolic one at Fig. 1a) for all of the areas of Antarctica where the melting described in today's post is taking place.

They are not merely symbolic graphs, they detail the actual melt conditions for areas all around Antarctica (like those I did to detail Antarctica glaciers; see Antarctica 2.0 - 6 and attachments  A, B, C, D, E, F).

These new graphs, calculated using the TEOS-10 library, also feature the new oceanographic depth levels I have begun to use (New Slang).

Here are the links to appendices containing those graphs A, B, C, D, E, F.

The previous post in this series is here.






Appendix A - West Indian Ocean

This page is an Appendix To Hot, Warm, & Cold Thermal Facts: Tidewater-Glaciers - 6 (click on a graph to enlarge it):


Depths

Locations

Fig. 1 CT & Melt @ Abissopelagic Depth

Fig. 2 CT & Melt @ Bathypelagic Depth

Fig. 3 CT & Melt @ Mesopelagic Depth

Fig. 4 CT & Melt @ Epipelagic Depth

Fig. 5 Absolute Salinity @ various Depths

Appendix B - East Indian Ocean

This page is an Appendix To Hot, Warm, & Cold Thermal Facts: Tidewater-Glaciers - 6 (click on a graph to enlarge it):


Depths

Locations


Fig. 1 CT & Melt @ Abissopelagic Depth

Fig. 2 CT & Melt @ Bathypelagic Depth

Fig. 3 CT & Melt @ Mesopelagic Depth

Fig. 4 CT & Melt @ Epipelagic Depth

Fig. 5 Absolute Salinity @ various Depths

Appendix C - Ross Sea

This page is an Appendix To Hot, Warm, & Cold Thermal Facts: Tidewater-Glaciers - 6 (click on a graph to enlarge it):


Depths

Locations


Fig. 1 CT & Melt @ Abissopelagic Depth

Fig. 2 CT & Melt @ Bathypelagic Depth

Fig. 3 CT & Melt @ Mesopelagic Depth

Fig. 4 CT & Melt @ Epipelagic Depth

Fig. 5 Absolute Salinity @ various Depths

Appendix D - Amundsen Sea

This page is an Appendix To Hot, Warm, & Cold Thermal Facts: Tidewater-Glaciers - 6 (click on a graph to enlarge it):


Depths

Locations



Fig. 1 CT & Melt @ Abissopelagic Depth

Fig. 2 CT & Melt @ Bathypelagic Depth

Fig. 3 CT & Melt @ Mesopelagic Depth

Fig. 4 CT & Melt @ Epipelagic Depth

Fig. 5 Absolute Salinity @ various Depths

Appendix E - Bellingshausen Sea

This page is an Appendix To Hot, Warm, & Cold Thermal Facts: Tidewater-Glaciers - 6 (click on a graph to enlarge it):


Depths

Locations



Fig. 1 CT & Melt @ Abissopelagic Depth

Fig. 2 CT & Melt @ Bathypelagic Depth

Fig. 3 CT & Melt @ Mesopelagic Depth

Fig. 4 CT & Melt @ Epipelagic Depth

Fig. 5 Absolute Salinity @ various Depths



Appendix F - Weddell Sea

This page is an Appendix To Hot, Warm, & Cold Thermal Facts: Tidewater-Glaciers - 6 (click on a graph to enlarge it):


Depths

Locations



Fig. 1 CT & Melt @ Abissopelagic Depth

Fig. 2 CT & Melt @ Bathypelagic Depth

Fig. 3 CT & Melt @ Mesopelagic Depth

Fig. 4 CT & Melt @ Epipelagic Depth

Fig. 5 Absolute Salinity @ various Depths