Oceanic excitation of the Chandler wobble using a 50-year time series of ocean angular momentum

Abstract

A 50-year time series of ocean angular momentum (OAM) is used to estimate the oceanic contribution to the excitation of the Chandler wobble. Our estimate of the oceanic excitation power, 18 mas2/cpy, is in good agreement with the residual excitation derived from a simultaneous use of polar motion and atmospheric angular momentum data, 21 mas2/cpy. Direct comparison of the OAM series and the inferred non-atmospheric excitation yields lower correlation and lower coherence at the Chandler frequency than in the study of Brzeziński and Nastula (2001) based on the shorter OAM series of Ponte et al. (1998). Differences in coherence levels are partly related to significant differences found in the two OAM series, indicating substantial dependence of OAM results on model and data assimilation procedures.