|Fig. 1 Golden Stations|
The "golden 23" (more or less) began as an effort associated with "the European problem."
That problem was the result, among other things, of researchers not knowing about a seminal paper explaining the earliest scientific awareness of the dynamics of ice sheet gravity and its impact on sea level change (On the robustness of predictions of sea level fingerprints).
That problem was also perpetuated by a lack of the knowledge of sea level change "fingerprints" which could be used to determine what ice sheet melt was causing observed sea level fall and rise (Calling All Cars: The Case of the "Missing Six" - 5).
II. Some Light Shines Through
Mitrovica also explained that previous scientific papers, as well as his own work, made it possible to use the records of certain tide gauge stations in order to derive an understanding of global sea level trends.
For a complete list, links, and other details of the zones and tide gauge stations, see "IV. The Data Sources" in the Dredd Blog post Calling All Cars: The Case of the "Missing Six" - 5.
III. The New Approach
Then I "went and did it", i.e, I stirred up some controversy about aspects of thermal expansion caused sea level change in a Dredd Blog series (On Thermal Expansion & Thermal Contraction, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18).
Among the arguments presented in that series is one that points out the dearth of evidence to support the assertion that "thermal expansion is the major cause of sea level rise in the 19th and 20th centuries."
During the discussion I had not used the golden 23 zones approach.
Instead, I tended to used the layered approach (see e.g. On Thermal Expansion & Thermal Contraction - 18).
So, the new approach today is to get back to the golden 23 realm, while keeping and using some of the tools and techniques developed during the use of the layered approach.
IV. One Useful Tool
One useful tool is the steric volume calculation algorithms that use the latitudes and longitudes of a WOD zone, along with average world ocean average depth, to calculate the volume of ocean water in that zone.
By also using temperature and sality change with the volume calculation, we can calculate the amount of volume increase and decrease of the ocean in that zone.
Comparing that and the pattern of the volume changes with sea level change patterns, we can see just how related or unrelated the steric (thermal expansion and contraction) changes are to the sea level changes.
V. Today's Graphs
In that light, I have used the golden 23 zones data from the World Ocean Database (WOD) in combination with the data from the Permanent Service For Mean Sea Level (PSMSL) tide gauge station records to generate some graphs.
The graphs at Fig. 3 - Fig. 7 are pattern tests.
The graphs at Fig. 2 and Fig. 8 are of the same data, however, the graph at Fig. 8 is a graph of the values from year to year, while the graph at Fig. 2 is a graph of the changes in that data from year to year.
|Fig. 9 Trend Change|
The pattern tests compare the mean averages (Fig. 8) with the calculated changes (Fig. 2), to see if the change patterns exactly match the mean average values.
If the patterns do not exactly match, then there is a problem with the software.
Since they do match, the software is ok, so I generated a golden 23 graph that compares values so as to consider the thermal expansion hypothesis mentioned earlier in Section III.
As you can see in the graph at Fig. 2, the sea level pattern in the first pane (upper left pane) does not match the steric, thermal expansion pattern in the fourth pane (lower right pane).
Interestingly, the graph at Fig. 9 shows that a trend change in global air temperatures also took place during that time frame.
Steric, thermal expansion is not the major cause of sea level rise in the golden 23 zones (the zones to watch for global sea level change trends), even though it may be more closely related to other climate factors.
Review the excellent presentation in the video below, by Dr. Mitrovica, if you like.