High-Spatial-Resolution Mass Rates From GRACE and GRACE-FO: Global and Ice Sheet Analyses

GRACE and GRACE-FO gravimetry data are unique in its ability to observe global water mass variability and has frequently been applied for the determination of global mass rates to quantify the impacts of climate change and human activity on global freshwater availability and land ice evolution. However, its relatively coarse spatial resolution of similar to 300-500 km at monthly intervals precludes its direct use to measure mass changes in smaller drainage basins and individual glacier systems. We present a new global high-resolution mascon product that improves spatial resolution and signal recovery by estimating trends directly from more than 16 years of Level 1B GRACE and GRACE-FO data. We compare this product to independent gravimetry spherical harmonic trend estimates and to ice sheet mass rates derived from ICESat and ICESat-2 laser altimetry. We demonstrate enhanced global signal recovery and improved agreement with ICESat/ICESat-2 and discuss likely causes for the remaining discrepancies between the gravimetry and laser altimetry solutions. Plain Language Summary The GRACE and GRACE-FO gravimetry missions uniquely observe the global movement of water and ice mass. Measuring the rates of these mass changes has been especially useful for quantifying and understanding the impacts of climate change and human activity on global freshwater availability and land ice evolution. However, the standard monthly data products from these missions are not able to spatially resolve smaller drainage basins and individual glacier systems. We present a new product that significantly enhances the spatial resolution of the mass change rates. This is accomplished by directly estimating the rates from more than 16 years of GRACE and GRACE-FO data. We analyze our new results globally and compare our ice sheet mass rates to those derived from ICESat and ICESat-2 laser altimetry measurements. We demonstrate that our new product: (1) improves the recovery of global mass change rates, (2) is capable of measuring mass rates for individual glacier systems, and (3) is useful for identifying the likely causes for the remaining discrepancies between the gravimetry and laser altimetry solutions.