Nearly three decades of laser altimetry reveal strong regional contrasts and glacier-driven ice losses in Greenland

The Greenland Ice Sheet, a major contributor to sea-level rise, loses mass through complex processes that are not fully understood. Laser altimetry provides direct and accurate measurements of ice sheet surface elevation. Here, we present the first continuous, laser altimetry-based annual reconstruction of Greenland Ice Sheet mass change from 1994 to 2020 at 1 km horizontal resolution. Our novel approach fuses NASA's multi-mission laser altimetry records and isolates dynamic ice thickness change. We estimate an average mass loss of 191 ± 6 Gt/yr, with the most intense thinning concentrated in western and southeastern regions, driven by enhanced surface melt and dynamic ice mass loss. Despite challenges in partitioning surface and dynamic components, we find a robust temporal evolution of dynamic thinning that reveals diverse thinning patterns across tidewater glaciers. This high-resolution reconstruction provides a crucial, observation-based benchmark for model calibration and evaluation that illuminates the complex drivers of ice sheet mass change across spatial and temporal scales.