Ice-sheet mass balance from satellite altimetry-gravimetry fusion

Global ice mass loss is the largest contributor to modern sea-level rise; however, its future contribution remains highly uncertain given our limited understanding of the mechanisms that drive change. Identification of regional ice mass changes is critical for precise quantification of spatially varying global sea-level change. Knowledge of regional signatures of major drivers may prove useful for understanding ice sheets' role in future sea-level changes. Here, we present a
novel approach fusing satellite gravimetry (GRACE-FO) and altimetry (ICESat-
2) observations using existing surface-process models to better constrain
poorly understood processes like firn densification and provide the first
observationally constrained partitioning of ice mass change into surface
mass balance (SMB) and ice dynamics. We generate spatial fingerprints of
SMB and firn air content variability through empirical orthogonal function
analysis, then invert for their associated principal components using monthly
GRACE-FO mass and ICESat-2 volume measurements as observational
constraints (December 2018-December 2024). This fusion approach
reconciles altimetric and gravimetric mass estimates while enabling high
spatial resolution attribution of change drivers.