Geophysical Excitation of the Chandler Wobble Revisited

The 14-month Chandler wobble is a free motion of the pole excited by geophysical processes. Several recent studies demonstrated that the combination of atmospheric and oceanic excitations contains enough power at the Chandler frequency and is significantly coherent with the observed free wobble. This paper is an extension of earlier studies by Brzezinski and Nastula (Adv Space Res 30:195-200, 2002), Brzezinski et al. (Oceanic excitation of the Chandler wobble using a 50-year time series of ocean angular momentum. In: Adam J, Schwarz K-P (eds) Vistas for geodesy in the new millennium. IAG Symposia, vol 125. Springer, Berlin, pp 434-439, 2002) using the same method of analysis but other available estimates of atmospheric and oceanic excitation of polar motion. We also try to assess the role of land hydrology in the excitation balance by taking into account the hydrological angular momentum estimates. Our results generally confirm earlier conclusions concerning the atmospheric and oceanic excitation. Adding the hydrological excitation is found to increase slightly the Chandler wobble excitation power, while the improvement of coherence depends on the geophysical models under consideration.