Orbital mechanics and the Chandler Wobble

Bob Grumbine


The Chandler Wobble is one of the largest periodic or quasi-periodic variations in the earth's orientation. While its forcing was resolved after over a century of research -- atmospheric circulation and induced ocean circulation and pressure -- the question of why there should be such forcing in the atmosphere has remained open. I suggest that variations in earth-sun distance is the source which provides this forcing to the atmosphere and thence ocean. Analysis of searth-sun distance, earth's orientation, and atmospheric pressure and winds shows a coherent relationship between the atmosphere and earth orientation at just those periods expected from the earth-sun distance consideration. As this is a general mechanism, it can be used in examining regular climatic variations on a wide range of periods and for climate parameters other than the earth's orientation.