IDENTIFICATION OF THE REGIME OF THE POLAR MOTION USING COORDINATE DATA FOR 1900-1990

Analysis of the spectral power-density function and the Poincar'e meth od are used to identify the type of motion exhibited by the Earth's po le from 1900-1990. The former method allows identification of a quasi- periodic regime with two main frequencies-annular and Chandler. The ex istence of combinational frequencies in this spectrum and the broadeni ng of the spectral peaks suggest a quasi-periodic regime making a tran sition to chaos. However, the appearance of a third independent freque ncy in the spectrum is necessary for such a transition. It is conclude d that the identification of the polar-motion regime over the time int erval considered is insufficient to predict the further evolution of t he system over arbitrarily long times.