On the variability of the Chandler wobble
The works that we carried out during the last ten years lead to significant progress inthe knowledge of the Chandler wobble (CW) of the Earth polar motion (PM). In Zotov and Bizouard(2012) we reconstructed the excitation of this resonant mode by using Panteleev’s correctivefiltering. Now we are sure, that this filtering is a regularizing algorithm asfar as its parameters areconsistently selected with the uncertainty affecting the resonance parameters and the observations.The excitation demonstrated a quasi 20-year amplitude modulation. In theframework of the firstorder differential linear equation describing the polar motion, it is easyto show that this modulationaccounts for the 40-year change of the CW amplitude as well as the splitting ofthe CW spectra.A simple model of the CW, composed of 80 and 40-year harmonics, accounts for the presentminimum in Chandler wobble amplitude, like in 1930s, and also predicts that its amplitude will startto increase in the nearest future with a phase shift ofπ. On the other hand, geodetic excitationof the CW well matches the ocean-atmospheric excitation (Bizouard, 2020) over recent 50 yearswith a dominant role of the ocean, producing the 20-year modulation. Thus, thephysical cause ofit could stem from climatic or tidal process influencing the oceanic circulation.