A Calculation Method of Marine Gravity Change Rate Based on Satellite Altimetry

The Gravity Recovery and Climate Experiment(GRACE) gravity satellites can only detect low-resolution marinegravity change. This study proposes to use satellite altimetrydata to construct high-resolution marine gravity change rate(MGCR) model. The marine gravity field change is mainlycaused by the seawater mass migration. Based on the sphericalharmonic function (SHF) method and mass loading theory,a spherical harmonic synthesis formula is constructed to cal-culate MGCR. This idea is utilized to establish MGCR modelin Arabian Sea (AS). First, the multisatellite altimeter datafrom 1993 to 2019 are grouped, preprocessed, and utilized toestablish mean sea-level models; then, the long-term altime-try sea-level change rate (SLCR) is estimated. Second, thealtimetry SLCR subtracts the effects of Steric and GlacialIsostatic Adjustment (GIA) to obtain the SLCR model caused bymass migration (AS_MM_SLCR). Finally, we perform sphericalharmonic analysis on AS_MM_SLCR and apply the sphericalharmonic synthesis formula to estimate MGCR model on 5 ' x5 ' grids (AS_SHF_MGCR). AS_SHF_MGCR has higher resolutionthan GRACE_MGCR, compensating for inability of GRACE todetect small-scale marine gravity changes; the MGCR mean ofAS_SHF_MGCR is 0.13 mu Gal/year, which indicates the long-termrising trend of marine gravity in AS. This letter proposes amethod for calculating the MGCR using satellite altimetry, whichoffers a novel approach for marine time-varying gravity research