An Observational Constraint for Future Greenland Rain in a Warmer Atmosphere

Abstract

Increased rain over the Greenland Ice Sheet can accelerate ice sheet mass loss and sea level rise. Here, 14 years of unique spaceborne-radar observations over the Greenland Ice Sheet provide an observational constraint on increased rain occurrence in a warming climate. Combining these satellite-based precipitation observations with near-surface temperature reveals the spatial and temporal distribution of modern (2006–2020) snow and rain. This distribution serves as the foundation for determining the increase in Greenland rain due to atmospheric warming alone. Rain doubles under 2.3°C of local near-surface warming. With 10.7°C of warming, half of all precipitation observations become rain. Projected 21st century warming would lead to a rain-dominated precipitation record at low elevations with rain possible anywhere on the ice sheet. These results suggest precipitation phase shifts due to warming alone can generate rain capable of amplifying surface runoff and sea level rise.