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Improved estimates of geocenter variability from time-variable gravity and ocean model outputs

by T. C. Sutterley and I. Velicogna
Remote Sensing, Special Issue "Remote Sensing by Satellite Gravimetry" (2019)

Abstract:
Geocenter variations relate the motion of the Earth's center of mass with respect to its center of figure, and represent global-scale redistributions of the Earth's mass. We investigate different techniques for estimating of geocenter motion from combinations of time-variable gravity measurements from the Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-On missions, and bottom pressure outputs from ocean models. Here, we provide self-consistent estimates of geocenter variability incorporating the effects of self-attraction and loading, and investigate the effect of uncertainties in atmospheric and oceanic variation. The effects of self-attraction and loading from changes in land water storage and ice mass change affect both the seasonality and long-term trend in geocenter position. Omitting the redistribution of sea level affects the average annual amplitudes of the x, y, and z components by 0.2, 0.1, and 0.3 mm, respectively, and affects geocenter trend estimates by 0.02, 0.04 and 0.05 mm/yr for the the x, y, and z components, respectively. Geocenter estimates from the GRACE Follow-On mission are consistent with estimates from the original GRACE mission.

Caption: Time series of recovered geocenter variations, (a) x, (b) y and (c) z, in mm calculated using an iterated self-consistent geocenter with self-attraction and loading effects from time-variable gravity fields provided by the Center for Space Research (orange), the German Research Centre for Geosciences (purple), the German Research Centre for Geosciences with pole tide coefficients replaced by values from Satellite Laser Ranging (blue) and the Jet Propulsion Laboratory (green). The gray dashed vertical line denotes when the accelerometer onboard GRACE-B was turned off in 2016. The gray shading denotes the period between the GRACE and GRACE-FO missions.
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