Thursday, August 2, 2018

The World According To Measurements - 19

General Ocean Temperatures
In the previous post of this series we looked at two polar zones, one Arctic the other Antarctic, and compared them one to the other.

They contrasted each another in various ways.

They also differ from zones nearer to the Equator as shown by the graphic to the left, which was also featured in that previous post (The World According To Measurements - 18).

I am featuring that generalization graphic again in today's post.

The two zones discussed in today's post are Equatorial zones 7016 and 5016, which have the same longitudes as the two former zones, but of course have different latitudes, one latitude being the Equator.

I am using the same general display layout of the graphs in the post which is three sections (Conservative Temperature, Absolute Salinity, and Thermosteric Sea Level Change).
Fig. 1a
Fig. 1b

The Conservative Temperature graphs are in section one (Fig. 1a and Fig. 1b), the Absolute Salinity graphs are in section two (Fig. 2a and Fig. 2b), and the Thermosteric Sea Level Change graphs are in section three (Fig. 3a and Fig. 3b).

The major addition today is section four, which contains the data values that were used to generate the graphs (Fig. 4a - Fig. 4b).

Fig. 2a
Fig. 2b
On to the discussion.

Notice that the Conservative Temperature graphs in section one (Fig. 1a and Fig. 1b), are the pattern suggested in the generalization graphic at the top of today's post.

That is not surprising in the sense that the two WOD Zones (7016, 5016) have a shared boundary, which is the Equator.

The Equator is the southern boundary of WOD Zone 7016 and the northern boundary of WOD Zone 5016 (one is in the Northern Hemisphere, the other is in the Southern Hemisphere).

The Absolute Salinity graphs (Fig. 2a and Fig. 2b) have a similar pattern as well, with some variation.
Fig. 3a
Fig. 3b

The Thermosteric Sea Level Change is another story (Fig. 3a and Fig. 3b) because the patterns have significant contrast.

That is surprising because the depth levels are of course identical.

I suspect that the differences are due to WOD Zone 7016 being north of WOD Zone 5016, and that could put them in different ocean current routes.

The year in which the in situ measurements were taken is 2016.

That year had some fluctuation that could have impacted the patterns as well (May 2016 El Niño/La Niña update, NOAA).

Another factor to consider is that the TEOS-10 calculations I make from the in situ measurements are quite specific, in the sense that the calculations are based on small mass units composed of depth slices.

Others may not use the same technique so they may miss this phenomenon.

I have been careful to use a fixed mass-unit value for depth measurements since a certain paper was published cautioning against less robust techniques:
One paper expands upon the proper techniques and procedures involved in steric vs eustatic analysis:
"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."
(JOURNAL OF GEOPHYSICAL RESEARCH: OCEANS, VOL. 118, 953–963, doi:10.1002/jgrc.20060, by Gabriel Jordà and Damià Gomis, 2013; @p. 953, 954, emphasis added).
(On The More Robust Sea Level Computation Techniques). What that means is that for each depth level volume slice (e.g. 10m to 20m, 250m to 300m) the volume of the water being impacted by the temperature measurements being used to calculate thermal expanson / contraction must be individually and specifically calculated.

Fig. 4a
That means that the 10m-20m slice must use a 10m "h" value  but the 250m-300m slice must use a 50m "h" value because the formula involved is: v = lwh.

Mixing the volume values will cause inaccuracies.

Furthermore, that volume value must not be changed during the entire time frame being calculated (e.g. 1968-2016).

Finally, the individual zone volumes must be independently calculated as well, because they don't have the same area (length x width) because they are latitude / longitude boundaries (which vary from place to place) on the globe.

The accurate calculation of "volume changes per mass unit" requires usage of the same mass unit (v = lwh) throughout the time frame that the particular calculations cover.

Fig. 4b
Calculating the thermosteric volume changes requires the usage of temperatures taken within the same mass-unit of seawater.

That is how I calculate the values shown in Fig. 4a and Fig. 4b.

I am "going by the book" as they say.

I think that is why I am generally at odds with the general hypothesis in vogue these days that "thermal expansion is the main cause of 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).

I am currently convinced that ice sheet and glacier melt water is the main cause of sea level rise, and in second place is the "ghost water" effect (NASA Busts The Ghost).

The previous post in this series is here.

1 comment:

  1. I like it when folks get together and share ideas. Great website, stick with it!