Friday, January 6, 2017

Axial Precession Induced Sea Level Change

Fig. 1 Southern Hemisphere bias

I. Background

The Earth's natural axial precession cycle causes natural climate change, which in turn causes natural sea level change (SLC).

The reason that SLC takes place is because the tilt of the hemispheres toward and away from the Sun reverses during a complete cycle of ~26,000 years (Fig. 1, Fig. 2).

The axial tilt causes a bias that favors one hemisphere for more solar exposure in one half of the cycle, then reverses to favor the other hemisphere for the remaining half of the cycle.

The bottom line during a complete axial precession cycle is that the hemispheres receive about equal solar exposure treatment once all is said and done.

These natural changes that take place do so very slowly, compared to the ongoing Anthropogenic (man-made) climate changes (due to the burning of fossil fuels).

Fig. 2  Northern Hemisphere bias
And the natural changes that take place, as a result of the axial precession, are not catastrophic compared to the ongoing man-made global warming.

II. When In Rome

The graph at Fig. 3 illustrates the cycle in traditional PSMSL RLR sea level change orientation.

Dr. Mitrovica pointed out (see video below if you haven't yet) that since Roman times, when the elites used fish tanks to store live fish for later consumption, sea level has not changed much (about 1m).

That is reflected in the relatively small increase/drop at the peak area of the graph.

That is not to say that the SLC is no big deal, because from the zero point to the high point it adds up to about 1700 mm, or about 5.58 ft.

Fig. 3 The number of years between dots is 2,160
That is not a great deal to handle over 13,000 years (0.13 mm yr) in terms of time to adapt.

It equates to the melting of only 2.1% of the total ice in the Earth's cryosphere (see USGS table; 80.32 m is 263.5 ft, cf. ghost water).

Note that this is an estimated SLC based on the previous temperature projections (When The Mayan Calendar Was Conceived); also note that the current sea level in some areas of the globe, as shown by Fig. 4, is at or above the highest level shown on Fig. 3.

III. Conclusion

Nevertheless, those civilizations that would survive for more than 13,000 years would have
Fig. 4 Current Sea Levels
to take care when they build seaports (e.g. Phoenicians), because it only takes about half of the axial tilt's SLC amount to take out a seaport (The Extinction of Robust Sea Ports, 2, 3, 4, 5, 6).

So, where would the "warning stones" be placed (e.g. Warning Stones) ?

So far our civilizations have not mastered this problem or even been aware of it ("In other words, a society does not ever die 'from natural causes', but always dies from suicide or murder --- and nearly always from the former, as this chapter has shown." - A Study of History, by Arnold J. Toynbee).

Have a good weekend.

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