Alexandre Couhert and Maxime Rousselet, both at Centre national d’études spatiales (CNES), Toulouse, France

will present

Part I (Alexandre):
Satellite altimetry sea level rise estimates and ocean mass trends derived from satellite gravimetry both rely on solid Earth/pole tides and GIA models, to remove these signals from GRACE/-FO and altimeter based sea surface height observations, and access to the secular variations in these global-scale mass transfers. In 2015, a concern was raised concerning the consistency of the recommended modeling approach in the International Earth Rotation Service (IERS) Conventions and updates were proposed since then to accommodate this issue. Nowadays, with hindsight, additional inconsistencies may arise when combining these different geophysical models.

Part II (Maxime):
Solid Earth models are crucial for interpreting space-geodetic observations, yet mantle rheology remains inconsistently treated across time-scales. A self-consistent framework must capture elastic, transient, and viscous deformation. In particular, the transient rheology below the asthenosphere, acting in the interannual to centennial band, remains poorly constrained. Previous studies estimated tidal-band attenuation from a-posteriori gravity fields, losing the covariance information contained in the observations. Incorporating rheology directly into orbit determination overcomes this limitation. What is the amplitude of the mantle’s transient response below the asthenosphere?
We address this by combining consistent orbit and rheology modeling with independent geophysical constraints. Analytical orbital perturbation theories describe satellite responses to anelastic pole tide and long-period zonal solid Earth tides, showing why these signals should be analyzed jointly. We use this framework to estimate Extended Burgers parameters, supported by a comprehensive error budget covering constellation design, formal uncertainties, other rheological parameters, and residual gravity-field errors.
We further assess implications for climate-related quantities derived from space geodesy. For GRACE/-FO estimates of barystatic sea-level change, rheological treatment can introduce a systematic trend bias exceeding 10%. This highlights the importance of transient mantle deformation for interpreting long-term satellite records and motivates a consistent solid Earth framework across time-scales for both mantle characterization and climate monitoring.