Impact of loading and thermoelastic deformation on estimates of non-linear geocenter motion derived from GNSS and SLR observations
Abstract
Seasonal mass redistribution of continental water, atmospheric pressure, and non-tidal oceanic loading deforms the Earth, inducing horizontal and vertical surface displacements of a few mm and a few cm respectively. In addition, long wavelength annual temperature variations induce a thermoelastic deformation field, with vertical surface displacements of a few mm. The longest wavelength of both effects, their spherical harmonic degree-1 component, not only deforms the solid Earth, but also induces geocenter motion between the Center-of-Mass of the total Earth system (CM) and the Center-of-Figure (CF) of the solid Earth surface.
SLR and GNSS station position time series used to retrieve geocenter motion are affected by surface loading and thermoelastic deformation. We propose to evaluate the impact of both effects on geocenter motion estimates by correcting the station position time series from a now well established physical loading deformation model, and by estimating the thermoelastic contribution at geodetic stations. On the one hand, we model surface displacements induced by variations in continental water, atmospheric pressure, and non-tidal oceanic loading derived from the Gravity and Recovery Climate Experiment (GRACE) for spherical harmonic degrees two and higher. On the other hand, we estimate the combined contribution of bedrock and monument thermal expansion to degree-1 deformation of stations network. We then compare results to physical models of bedrock thermoelastic deformation as the response of a realistic Earth rheological model to land surface temperature variations (NOAA) and of average monument thermal expansion. We compare and discuss non-linear geocenter motion derived separately from SLR (using the network shift approach) and GNSS (using the degree-1 deformation approach) and discuss the impact of loading and thermoelastic effects on both estimates. We finally discuss the agreement and discrepancies between recent independent estimates of non-linear geocenter motion.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.G42A..03C
- Keywords:
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- 1229 Reference systems;
- GEODESY AND GRAVITYDE: 1299 General or miscellaneous;
- GEODESY AND GRAVITY