Anomalies of the Chandler Wobble in 2010s

The Earth's rotation is nonuniform: the position of the pole drifts and describes circles with the annual and Chandler (433 days) periods; the Earth's rotation velocity also varies. In the beginning of 2000s, the amplitude of the Chandler wobble began to decrease and in 2017-2020 reached a historical low comparable only with the low of late 1920s. We extract the Chandler time series by different methods (removal of the trend and annual oscillation, Panteleev filtering, and others) from series of EOP C04 and EOP C01 data on the polar motion and demonstrate that its phase also varies from early 2010s. Such variation in the phase occurred in the 1920s-1940s and equaled pi rad; at present, it approaches 2 rad. Possible interpretations of the phenomena, their manifestations in the polar motion spectrum, and probable causes are discussed.