The Chandler Wobble

In Chapter 13 of the book, we have a description of the mechanism causing the Chandler wobble of the Earth’s polar axis.   Last fall, NASA updated a description of their understanding of the axis drift [1] described here, which we can place in context with the model …

Data for the Chandler wobble is located here. Taking the first derivative of the Y position (which also removes the drift component), we can plot the data and fit the lunisolar declination forcing model to that data.

Using a short training interval from 1950 to 1962.5 (click to enlarge):

The amplitude spectrum over that interval matches quite well:

The correlation to the out-of-band validation intervals is quite good up to the present:

In the future, we can continue to track the Chandler wobble and observe if it continues that predicted by a lunisolar forcing.


[1] S. Adhikari et al., “What drives 20th century polar motion?,” Earth and Planetary Science Letters, vol. 502, pp. 126–132, Nov. 2018.





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