The Gravity of Sea Level Change - 2

Fig. 1  Zones of Influence

Some have criticized The Gravity of Sea Level Change and related Dredd Blog System posts concerning sea level change (SLC).

That criticism has been done out of ignorance.

The series concerning the study of ignorance generators within society has shown that, clearly, ignorance is an epidemic in the U.S.eh? these daze (Agnotology: The Surge, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17).

Anyway, the science of the gravity of SLC is well established and non-controversial to non-ignorant scientists and laypeople alike:

Modern melting of land ice affects sea level along the west coast of the United States in two ways. First, the large mass of glaciers and ice sheets generates an additional gravitational pull that draws ocean water closer, raising relative sea level near the ice masses. As the ice melts, the amount of ice mass on land declines, decreasing its gravitational pull on the ocean water. The loss of

Fig. 2  Gravity is a weighty matter

mass also results in uplift of the land mass under the ice. The combination of these effects causes relative sea level to fall in the vicinity of the ice mass. The fall extends, at decreasing rates, in the region within a few thousand km of the melting ice. Second, ice melt enters the ocean, raising global mean sea level. Because of gravitational and deformational effects, however, the distribution of new ice melt is nonuniform over the globe. Relative sea level falls near the shrinking ice mass and rises everywhere else. This effect is shown schematically in Figure 4.8. The combined effect of new water mass entering the ocean and altered gravitational attraction results in a spatial pattern of sea-level rise that is unique for each ice sheet or glacier (Mitrovica et al., 2001; Tamisiea et al., 2003). As a consequence, these sea-surface geometries have come to be known as sea-level fingerprints. Only a few studies have attempted to map the sea- level fingerprints of melting land ice along the west coast of the United States (e.g., Tamisiea et al., 2003, 2005).

(Sea-level Rise @ West Coast, book page 65, PDF page 66). The focus on the gravity of sea level change phenomenon has even led to a "fingerprinting" technique:

To estimate the effect of fingerprinting from these three ice masses on relative

Fig. 3 "Book 'em Danno"

sea level, it is necessary only to multiply the global sea-level equivalent of the mass loss from each source by the appropriate scale factor (colored contours) indicated in the figure and then add the contributions from all three sources. Scale factors greater than 0 indicate that the sea-level fingerprint increases relative sea-level rise at that location, and scale factors greater than 1 indicate that the rise is higher than the global sea-level equivalent value. Scale factors less than 0 mean that the effect of mass loss from a source causes the relative sea level to fall.

(ibid, cf. Tamisiea 2003, PDF). There are already many articles on Dredd Blog which demonstrate various aspects of the not-well-known phenomenon (see here under the heading "SEA LEVEL CHANGE").

In today's post I am announcing an enhancement to the Dredd Blog SLC software model.

That enhancement is to implement the fingerprinting dynamic, and apply it to each PSMSL tide gauge station.

What it will do, if all goes well, will be to calculate the percentages of influence on sea level rise (SLR) and sea level fall (SLF) that each ice sheet (or other ice mass location around the globe) will have on each SLC zone.

The graphic at Fig. 1 shows a modified version of the global zones Dredd Blog uses for reference (Databases Galore - 11).

That zone grid graphic has been modified by placing dark blue squares at the center of Zones "ak" (Gulf of Alaska) and "ab" (Scandinavia), and red squares at several ice mass locations (Svalbard, Glacier Bay Alaska, Greenland, and Antarctica).

Then, purple lines are drawn from the ice mass locations (i.e. from Antarctica, Greenland, and Glacier Bay) to the centers of Zones "ak" and "ab" to indicate influence on SLC in those zones.

In other words, those zones are going to have varying degrees of SLR and SLF at various and sundry times, of varying degrees.

That is the dynamic "fingerprint" being talked about by scientists in the know on this important subject.

When the software enhancement is completed, the model can show not only the historical fingerprint down through time, but will be able to also project the future fingerprint expected, for example, by the IPCC and by Hansen.

The benefit to those with boots on the streets of endangered areas (coastal zones) is that they can ascertain what is happening in their particular area.

That is better than relying on the mystical global mean average, a number that is not going to happen to any area in particular.

It is merely a figure of scientific speech that does not really tell you anything specific, like the mean average number of deaths is "xxxx" compared to the exact number of deaths in your town: yyyy (local values matter).

Anyway, first I will build a database table containing calculations to the center of each zone, then extrapolate from that to each tide gauge station in that zone.

Thanks to latitude and longitude figures already provided for each tide gauge station (by PSMSL), and thanks to latitude and longitude distances contained within the actual latitude and longitude values (leaving us to merely do some simple mathematical calculations).

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