Contributions of thermoelastic deformation to seasonal variations in GPS station position

Abstract

We investigate surface displacements due to land temperature variation with the 2014 global thermoelastic model, which is a solution on a uniformly elastic sphere under the constraint that the geocenter remains stationary. In this research, the seasonal variations of global surface displacements are numerically simulated based on 0---10 cm underground land surface temperatures from National Oceanic and Atmospheric Administration. The displacements include vertical and horizontal components for the first time. Meanwhile, the annual contributions of geophysical sources, which are mainly due to atmosphere, ocean, snow and continental water, are also estimated. For comparative analyses, the partial displacement by annual mass-loading and the total displacement by the combined annual of thermoelasticity and mass-loading are calculated, respectively, and displayed against the annual displacements at stations of global positioning system network. Results of the numerical simulation show that the amplitude of surface thermoelastic deformation is at the millimeter level on the global scale, topped at about 3 mm for radial displacement and about 1.5 mm for transverse components, which need to be considered for the high-precision terrestrial reference frame. The combined deformation caused by thermoelastic and mass-loading can explain the seasonal GPS observations better than the mass-loading alone, in particular for the transverse displacements.