Deformation induced by polar motion

Abstract

Variations in the geocentric position of the earth's rotation axis (polar motion) cause deformation within the earth. The effects of this deformation on radial and horizontal positions of points on the earth's surface, on baseline lengths between those points, and on surface gravity are estimated. The effects of the oceans and of the earth's anelasticity on this deformation are found to be negligible. Peak-to-peak variations in radial motion are typically 10-20 mm over a year. Horizontal displacements are less than 7-8 mm. Variations in baseline length can be as large as 30-40 mm. Variations of up to 13 microgal in surface gravity are possible. These numbers are all small enough that they can probably not be used to learn about the earth. However, they are large enough to affect noticeably present high-quality geodetic observations.