Saturday, July 28, 2018

On The More Robust Sea Level Computation Techniques - 10

Fig. 1a
Fig. 1b
Fig. 1c
Fig. 1d
Fig. 1e
In a previous post in another series (The World According To Measurements - 17), I cited to a fairly recent paper that discussed a portion of the World Ocean Database (WOD).

That paper discussed the WOD records concerning the Arctic Ocean area  (WOD Arctic, PDF).

In today's post I want to caution professional and amateur researchers alike about the hazards of that form of specialization as it relates to comprehensive conclusions.

To start the show while emphasizing that point, let's look at thermosteric sea level change (a.k.a. thermal expansion / contraction) in the four graphs (Fig. 1a - Fig. 1d) of the four quadrants of the world ocean (NE, NW, SE, SW).

Then let's look at the mean average of those four (Fig. 1e).

The graphs at Fig. 1a - Fig. 1e were each made using the same TEOS-10 library functions to calculate results from in situ measurements stored in the WOD.

Those measurements were processed to produce Conservative Temperature (CT), Absolute Salinity (SA), and Pressure (P).

This computation took place at each one of 33 WOD depth levels (if they contained measurements).

The boundaries of the depth levels are: 0m, 10m, 20m, 30m, 50m, 75m, 100m, 125m, 150m, 200m, 250m, 300m, 400m, 500m, 600m, 700m, 800m, 900m, 1000m, 1100m, 1200m, 1300m, 1400m, 1500m, 1750m, 2000m, 2500m, 3000m, 3500m, 4000m, 4500m, 5000m, and 5500m plus.

Those levels (horizontal slices) contain the volume or quantity of seawater, which is also an essential element of the calculations.

In other words, to calculate volume change caused by temperature change one has to know both the amount of volume at issue as well as the amount of temperature change.
Fig. 2a
Fig. 2b

As you can see, some of those levels / volumes are 10m in height (e.g. 0-10m, 20-30m), some are 20m in height (e.g. 30-50m), and so on.

The resulting graphs at Fig. 1a - Fig. 1d are quite different from one another even though the exact same process generated them.

At the end of the process, the four quadrants were added together and averaged to form the final graph at Fig. 1e.

We can see that it would not be accurate to say that any one of the five graphs represent the whole story, because they actually show that the ocean varies quite a bit from location to location.

That is true even in mean average cases, because the CT, SA, and P vary with depth, as shown in the graphs at Fig. 2a and Fig. 2b.

Fig. 3a
Fig. 3b
Fig. 3c
Fig. 3d
Fig. 3e
In that case, neither the top layer CT nor the top layer SA are the greatest value of that type at that location.

The top level depth has the lowest SA but not the lowest CT.

At another location it may be reversed, so generalizations have to be done carefully.

For example, to say "sea level is rising" is not true everywhere, because there are many locations around the globe where sea level is falling (see e.g. The Gravity of Sea Level Change, 2, 3, 4, NASA Busts The Ghost).

The most critical thing as far as I am concerned is the granularity of the measurements applied to the particular research being done at any given time.

The graphs at Fig. 3b - Fig. 3e are generated from the 30-50m slice of the ocean in the four quadrants.

The average of those quadrants is shown in Fig. 3a.

Here again, over generalization is risky, but we can say that the CT and the thermal expansion have the same general pattern in all situations graphed in this case.
Fig. 4

It would be risky, however, to say that the pattern shown at that depth level holds true in all locations and depths at all times.

That is why we continue to measure, monitor, and graph data for readers.

The work is not done for us, it is done for you readers.

Nevertheless, it is enjoyable to be able to share the hard work done by the men and women who are gathering measurements for us.

Take care, and keep alert, because there is more data down there (see Fig. 4 for an example of more depth information to come).

The previous post in this series is here.

"I want to fly like an eagle, to the sea ..."

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