Greenland Ice Sheet Runoff Observed by Multiple Satellite Radar Altimeters From 1992 to 2023

Runoff, a critical component of Greenland Ice Sheet (GrIS) mass loss, significantly influences global sea-level rise. However, quantifying its long-term variability remains challenging due to limited observational records. In this study, we obtain the longest continuous satellite-observed runoff (1992–2023) by integrating multiple satellite radar altimeters (ERS-1/2, Envisat, CryoSat-2) into a 32-year GrIS surface elevation time series. Building upon previous works, our key methodological improvements include refined intermission bias corrections and a unified approach to separating runoff-induced elevation changes across both ablation and inland runoff zones. Our results reveal a persistent GrIS runoff increase (4.24 Gt/yr) over three decades, with five consecutive high-runoff years since 2019. Notably, exceptionally high runoff occurred in 2012, 2019, and 2021, which were potentially linked to the North Atlantic Oscillation, anticyclonic conditions, and atmospheric river, respectively. Comparisons with regional climate models (RCMs) show strong agreement in interannual variability ($R^{2}\geq$ 0.83), while also identifying two significant findings: first, summer extreme snowfall causes satellite-observed runoff to be significantly underestimated; and second, satellite-RCM runoff differences are pronounced below 500 m elevation. These findings provide two critical insights for future research on satellite-observed runoff.