Summer Extreme Rainfall Events Intensify Southern Greenland Ice Sheet Melt

Rainfall events over Greenland ice sheet (GrIS) have become more frequent in recent decades. Several observed extreme rainfall (ER) events are accompanied by high GrIS surface melt. However, their role in surface energy budgets and the associated physical mechanisms remain poorly understood. Here we employ a surface energy balance (SEB) model to quantify the relative contributions of energy terms to surface melt energy (Qm) during ER events at QAS_L and QAS_U stations in southern GrIS. We further investigate the energy anomalies in terms of synoptic-scale atmospheric conditions during ER events lasting three or more days (ER+3d). Our results indicate that during ER+3d events, nonradiative energy contributes 54% of Qm at QAS_L, near the ice sheet margin, with turbulent fluxes serving as the primary energy source. In contrast, at QAS_U, closer to the equilibrium line, Qm remains dominated by radiative energy, accounting for 61% of Qm. The contribution of rainfall heat flux remains small, at approximately 4% at QAS_L and 2% at QAS_U. Rainfall-related atmospheric conditions trigger positive anomalies in turbulent fluxes and net radiation, due to strengthened cloud radiative forcing and increased turbulence scales in the near surface, which collectively contribute to high surface melt during ER+3d events. Therefore, the increased rainfall events have the potential to exacerbate surface mass loss by adding excess radiative and turbulent energy inputs in the future.