Secular Variations of the Zonal Harmonics and Polar Motion as Geophysical Constraints

Monitoring temporal changes in geodetic constants remains an important challenge for space geodetic investigations where the accurate determination of the effect significantly lags geophysical modeling requirements and inferences. For example, temporal changes in the Earth’s gravity field are manifestations of complex geophysical processes; an accurate determination of these changes can provide important insights and constraints on their underlying causes. The temporal variations of the external gravitational field represent a dynamic aspect of the mass redistribution within the combined solid-Earth/ocean/atmosphere system. Conservation of angular momentum for the system as a whole imposes constraints on the variations of the angular momenta of its various components. Coincident monitoring of the temporal variations of the geopotential, the Earth’s pole position, and its rotation rate are important objectives which can provide insight into key geophysical processes and the unique structure of the Earth itself.