Empirical mode decomposition of long-term polar motion observations

Abstract

We use the Empirical Mode Decomposition (EMD) method to study the decadal vari- ations in polar motion and its long–term trend since year 1900. The existence of the so–called “Markowitz wobble”, a multidecadal fluctuation of the mean pole of rota- tion whose nature has long been debated since its discovery in 1960, is confirmed. In the EMD approach, the Markowitz wobble naturally arises as an empirical oscillatory term in polar motion, showing significant amplitude variations and a period of approxi- mately 3 decades. The path of the time–averaged, non–cyclic component of polar motion matches the results of previous investigations based on classical spectral methods. How- ever, our analysis also reveals previously unnoticed steep variations (change points) in the rate and direction of secular polar motion