Interannual polar motion with relation to the North Atlantic Oscillation

Abstract

The North Atlantic Oscillation (NAO) is an interannual, north–south seesaw in the atmosphere and ocean. The associated motion and mass redistribution will inevitably cause variations in the Earth's polar motion. The present paper studies the relation of NAO with interannual polar motion. Two monthly series for the period of 1964–1994 are employed: the NAO index (NAOI), which is used as a proxy to measure the intensity of NAO, and the polar motion series. The latter is further processed to obtain the interannual polar motion excitation function ψ by deconvolution and subsequent removal of the drift, the seasonal terms and short period variations. The time-domain cross correlation and frequency-domain coherence studies show significant correlations between NAOI and ψ, especially on the x-component of ψ as anticipated from the general pattern of NAO. This suggests possible significant contribution of NAO in exciting interannual polar motion.