Uplift of the Tibetan Plateau: How to Accurately Compute the Hydrological Load Effect?

Abstract

AbstractThe uplift state of the Tibetan Plateau (TP) is determined by tectonic displacement and hydrological load displacement. However, it is unknown how much the load effect contributes to the uplift of the plateau. Typically, the vertical displacement due to the mass load is calculated based on the Gravity Recovery and Climate Experiment (GRACE) data and the spherical harmonic analysis method. However, because the GRACE data are truncated at lower harmonic degrees and tectonic mass changes are contained in the GRACE‐derived mass changes, the validity of using GRACE data to estimate the load displacement of the TP is questionable and needs further discussion. This study presents a reasonable approach to computing the loading effect by considering the global hydrological mass budget (seawater, lake, glacier, river, snow, soil water, canopy water, and groundwater). The TP's mean vertical load displacement rate we obtained is 0.15 mm/yr, contributing to 16 percent of the average TP uplift rate. Comparing the hydrologically computed load displacements and the GRACE‐derived load displacements indicates that the GRACE‐derived displacement differs significantly from the real hydrological load displacement. That is, we found that the GRACE‐derived load effect cannot be applied to correct the Global Positioning System (GPS) displacement, but the one computed with hydrological data works well. We claim that the load displacement effect for any GPS station should be calculated by Green's function method based on global hydrological data. Finally, we present a distribution map of the valid load vertical displacement of the TP and the load displacement correction for all the collected GPS stations.