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.





3 thoughts on “The Chandler Wobble

  1. So I read your research regarding wobble compared to ENSO and SOI, very interesting.
    I hope that I can continue to ask clueless ill formed questions. Like this one.
    Do you believe NASA JPL’s explanation of Chandler’s drift to be accurate?


    • I don’t care much about drift since it is a low energy forcing, much like the drift in length-of-day observations. You can spend all your time looking at that and miss the high-energy torquing required in the faster cycling.


      • I’ll look for that when I get a chance to increase the resolution of your plots to a year to year or decade. When dealing with observational science…what you are doing is absolutely fundamental to real science. Without mathematical predictions there is no understanding, my opinion as worthless as it is.
        One follow on is when I posted a simple comment “No Need for Newton here”, why did you assume that was directed at your theory, and not the hammer thrower and sea bed pressure theory?
        Like two extremely dissimilar masses would co-orbit. (again not a physicist so the term co-orbit may be misused what I mean is the earth and moon do not orbit each other as in the example of the hammer thrower). That is like asking what would happen if the earth let go of the moon? How far would the moon go?
        And another stupid question does the sun spin; possibly creating a gravitational period that would be similar to a standing wave affecting lunar forcing? Could that be a factor in torquing, and give an additional longer harmonic to the wobble period? Hope I asked that correctly cause I got this image in my head of a spiral gravity force emitting from the sun.


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