The glacier changes in the Alps from the GRACE and GRACE Follow-On Missions

In this study, we analyze glacier mass changes in the Alps using time-variable gravity field data from the Gravity Recovery and Climate Experiment (GRACE) and its successor, GRACE Follow-On (GRACE-FO), spanning from April 2002 to September 2023. A new method that incorporates vertical surface displacement data is employed to correct the glacial isostatic adjustment (GIA) and uplift signal. We apply three forward modeling schemes to recover the signals from GRACE/GRACE-FO observations. Our findings, compared with the annual glacier mass balance reported by the World Glacier Monitoring Service (WGMS), show that correcting uplift effects using land uplift data is more effective in the Alps. This method reveals that mass increases due to vertical displacement signals at 0.75 ± 0.11 Gt/yr, as opposed to the -0.39 ± 0.2 Gt/yr trend suggested by the GIA model ICE-6G_D. Among the three experimental schemes, the global unconstrained forward modeling algorithm proves the most accurate in estimating glacier mass change in the Alps. By applying our new uplift correction method, we determine the total glacier mass loss rate in the Alps to be -2.69 ± 0.65 Gt/yr using GRACE Level-2 data and -3.66 ± 0.21 Gt/yr using Mass Concentration (Mascon) solutions. Additionally, our research identifies a three-month lag between land surface temperature and glacier mass variations, reinforcing the reliability of our glacier mass change estimates.