The Chandler Wobble (CW) period is considered a single time-invariable
constant, ~1.2 years, but the possible time-variability
has not been examined using modern space-geodetic data. We first
examined whether the Chandler period could vary with time on the
assumption of minimum excitation power. Unexpectedly, the estimated
Chandler period has been shortened by more than 60 days since about
2005. Moreover, by simple least-squares modeling, we found that CW
started to be weaker in 2005 and almost disappeared in 2015. We
interpret these results in both excitation and wobble domains as caused
by the absence of CW for the first time in the observation history.
Assuming no excitations of CW since 2005, the rather abrupt damping
suggests the Q-value is below 25. Meanwhile, the analyses of the
available atmospheric and oceanic angular momentum (AAM/OAM) functions
indicate the significant amplitude of CW even after 2005, implying that
the AAM/OAM functions are incomplete.