Worldwide rivers annually export about 19 Gigatons of sediments to the ocean that mostly accumulate in the coastal
zones and on the continental shelves. This sediment discharge testifies of the intensity of continental erosion
and records changes in climate, tectonics and human activity. However, natural and instrumental uncertainties
inherent to the in-situ measurements of sediment discharge prevent from conclusive estimates to better understand
these linkages. Here we develop a new method, using the Gravity Recovery and Climate Experiment (GRACE)
satellite data, to infer mass-integrative estimates of sediment discharge of large rivers to the ocean. GRACE satellite
provides global gravity time series that have proven useful for quantifying mass transport, including continental
water redistribution at the Earth surface (ice sheets and glaciers melting, groundwater storage variations) but has
been seldom used for monitoring sediment mass transfers so far. Here we pair the analysis of regularized GRACE
solutions at high spatial resolution corrected from all known contributions (hydrology, ocean, atmosphere) to a
particle tracking model that predicts the location of the sediment sinks for 13 rivers with the highest sediments
loads in the world. We find that the resulting GRACE-derived sediment discharges off the mouth of the Amazon,
Ganges-Brahmaputra, Changjiang (Yangtze), Indus, Magdalena, Godavari and Mekong rivers are consistent with
in-situ measurements. Our results suggest that the lack of time continuity and of global coverage in terrestrial
sediment discharge measurements could be reduced by using GRACE, which provides global and continuous data
since 2002. GRACE solutions are regularly improved and new satellite gravity missions are being prepared hence
making our approach even more relevant in a near future. The accumulation of sediments over time will keep
increasing the signal to noise ratio of the gravity time series, which will improve the precision of the GRACE-
derived sediment discharges values.
Using three months of GPS satellite‐to‐satellite tracking and accelerometer data of the CHAMP satellite mission, a new long‐wavelength global gravity field model, called EIGEN‐1S, has been prepared in a joint German‐French effort. The solution is derived solely from analysis of satellite orbit perturbations, i.e. independent of oceanic and continental surface gravity data. EIGEN‐1S results in a geoid with an approximation error of about 20 cm in terms of 5 × 5 degree block mean values, which is an improvement of more than a factor of 2 compared to pre‐CHAMP satellite‐only gravity field models. This impressive progress is a result of CHAMP's tailored orbit characteristics and dedicated instrumentation, providing continuous tracking and direct on‐orbit measurements of non‐gravitational satellite accelerations.
