Elastic Displacement of the Solid Earth and GRACE/GRACE-FO response to variations in Global Lake and Reservoir Storage

Data from both the Gravity Recovery and Climate Experiment (GRACE/GRACE-FO) and displacements of Global Navigation Satellite Systems (GNSS) stations have been shown to provide a valuable record of variations in global terrestrial water storage. However, both satellite gravimetry and GNSS station displacements have trouble distinguishing between different components of water storage. The effective horizontal resolution of GRACE/GRACE-FO spreads concentrated surface water storage over a large area increasing the difficulty of determining the contribution of each component of water storage, and the displacement of any single GNSS station can be caused by a variety of physical phenomenon. To improve our understanding of water storage estimates from inversions of GRACE/GRACE-FO and GNSS station displacements here we use the monthly lake water storage anomalies of 287 natural lakes and 704 reservoirs, larger than 100 km², between October 1992 to October 2020 derived from satellite altimetry and Landsat imagery from the Global database of Lake Water Storage to predict the elastic deformation of the solid Earth and mass change observed by GRACE caused by these changes in lake water storage (Yao et al., 2023). We estimate the least-squares seasonal oscillation of each water body and combine it with a linear interpolation to construct a continuous monthly record across the study period. We estimate that our final product accounts for ≈68% and ≈66% global natural lake and reservoir storage respectively, with the worst coverage above 55°N where the temporal coverage of lake altimetry is poor. When removed from GRACE/GRACE-FO terrestrial water storage estimates the affected mascon’s WRMS is reduced by up to ≈38 cm equivalent water thickness (86%), with an average RMS reduction of 2 cm (11%). The elastic vertical displacements due to changes in lake and reservoir storage significantly affect 1885 GNSS stations and reduce the WRMS of vertical displacement timeseries by up to ≈28 mm (69%) with an average improvement of ≈1.2 mm (7%). GNSS stations experience a range of vertical displacement due to changes in lake water storage between 47 mm of uplift and 27 mm of subsidence with the largest variations found for stations around the Caspian Sea, the Great Lakes, and the Rift lakes of East Africa.