Estimation of the gravimetric pole tide by stacking long time-series of GGP superconducting gravimeters

International audienceWe compute the gravimetric factor at the Chandler wobble (CW) frequency using time-seriesfrom superconducting gravimeters (SG) longer than a decade. We first individually processthe polar motion and data at each individual gravity station to estimate the gravimetric factoramplitude and phase, then we make a global analysis by applying a stacking method todifferent subsets of up to seven SG stations. The stacking is an efficient way of getting ridof local effects and improving the signal-to-noise ratio of the combined data sets. Using thestacking method, we find a gravimetric factor amplitude and phase of 1.118 ± 0.016 and−0.45 ± 0.66 deg, respectively, which is smaller in amplitude than expected. The sources oferror are then carefully considered. For both local and global analyses, the uncertainties onour results are reliably constrained by computing the standard deviation of the estimates of thegravimetric factor amplitude and phase for increasing length of the time-series. Constraintson the CW anelastic dissipation can be set since any departure of the gravimetric factor fromits elastic value may provide some insights into the dissipative processes that occur at the CWperiod. In particular, assuming given rheological models for the Earth’s mantle enables us tomake the link between the gravimetric factor phase and the CW quality factor