Geodetic study on earth surface loading with GNSS and GRACE

Ice, snow, and liquid water on the surface of the Earth exert downward force onto the solid earth and deform the lithosphere typically in seasonal timescale. Space techniques, such as Global Navigation Satellite System (GNSS), made it possible to directly measure subtle displacements caused by loading. We can also observe such loads with time-variable gravity using gravity recovery and climate experiment satellites. These techniques made surface loads an attracting scientific target of modern geodesy. In this paper we briefly review the history of geophysical studies of surface loads through geodetic observations of crustal deformation and time-variable gravity. We also review advanced topics such as short-term crustal deformation due to severe meteorological episodes and monitoring of terrestrial water storages. We also present a few related topics such as the change of the obliquity of the Earth due to loads and artificial crustal subsidence signals caused by snow accretion onto GNSS antenna radomes.