THE SOURCE OF THE VARIABLE CHANDLER WOBBLE

International audiencen the absence of forcing, the Chandler wobble (CW) would have a period of 430.3 days, and would lose most of its energy after a few decades because of dissipation in the mantle and in the oceans. Observation of the Earths polar motion, however, reveals a prograde oscillation of which pseudo period can be as far as 20 days from the above value (Vondrak 1988). It gains energy at some epochs (Danjon & Guinot 1954) so that it never disappears. The CW excitation is accounted for, on average, by the atmosphere and oceans (Gross 2000, Brzezi ́nski & Nastula 2002), but its variability is so far poorly explained. We attempt to interpret it as consequence of the hydro-meteorological forcing, as suggested by Plag (1997),Celaya et al. (1999), and Seitz & Schmidt (2005)