Oceanic excitation of the chandler wobble

Abstract

We estimate the oceanic contribution to the excitation of the Chandler wobble using an 11-year time series of ocean angular momentum. The time domain comparison of this series with the non-atmospheric excitation inferred from the polar motion and atmospheric angular momentum data shows a high correlation over most of the period of 1985 to 1996 when they overlap. The frequency domain comparison yields a high coherence in the vicinity of the resonant Chandler frequency. In terms of the free wobble excitation power, we compute the ocean contribution to be 11.9 mas 2/cpy, which is approximately the same amount as supplied by the atmosphere. The combined action of the atmosphere and oceans provides about 80% of the power needed to maintain the wobble observed during 1985 to 1996, with the remaining deficit being at the level of one standard deviation of the excitation power estimated from a 100-year record of polar motion data.