Monthly Gravity Field Solutions From Early LEO Satellites' Observations Contribute to Global Ocean Mass Change Estimates Over 1993∼2004

Abstract

Since few time-variable gravity field models were developed before the Gravity Recovery and Climate Experiment (GRACE) era, one normally estimates the global mean ocean mass (GMOM) changes by summing the mass contributions. In this study, new monthly gravity field models named Tongji-LEO2021 developed from Early Low Earth Orbit (LEO) satellites' observations are used to directly estimate GMOM changes and quantify the closure of global sea-level budget with Altimetry and Steric observations between 1993 and 2004. The resulting GMOM changes from Tongji-LEO2021 solutions are comparable to those from the Center for Space Research RL06 GRACE solutions and the IGG-SLR-HYBRID solutions, with the correlation coefficients of 0.91 and 0.88. Our results show that the LEO-derived GMOM change rate is 0.88 ± 0.16 mm/year, slightly larger than 0.83 ± 0.16 mm/year from IGG-SLR-HYBRID, which are both close to Altimetry-Steric estimate (0.87 ± 0.33 mm/year). Overall, Tongji-LEO2021 solutions can estimate the GMOM change and understand the global sea-level change before the GRACE era.