Causes of fluctuations in the rotation of the Earth

Abstract

Over the last decade considerable progress has been made in closing the gap between geophysical theory and the observed changes in the Earth's spin rate and polar motion, which are affected by the Earth’s internal structure, properties and processes. New observational techniques and data have had a marked impact on understanding the short-term variations in the length of day and pole position, but we can expect between another 5 and 30 years to pass before they permit improved explanations of longer-term phenomena (18.6 year tidal effects, the Markowitz wobble, decade fluctuations in the length of day, etc.) This review summarizes recent advances, problems newly illuminated by recent Earth rotation data (for example mantle anelasticity, core-mantle coupling) and problems still unresolved.