Geocenter Motion

Geocenter motion refers to the temporal displacement of the Earth’s center of mass (CM) relative to the center of figure (CF) of the solid Earth. It is caused by mass redistribution within the Earth system, including variations in the atmosphere, oceans, hydrosphere, and cryosphere. These mass changes shift the location of the Earth’s center of mass by several millimeters over seasonal to interannual time scales.

In geodesy, geocenter motion is a critical parameter in the realization of terrestrial reference frames such as the ITRF, whose origin is defined at the Earth’s center of mass. Accurate determination of geocenter motion, primarily from satellite laser ranging (SLR) and GNSS, is essential for consistent station coordinates, sea level studies, gravity field modeling, and Earth system monitoring.