Variations in Greenland surface melt and extreme events from 1958 to 2023

Abstract

Surface melt and subsequent runoff have been the main contributors to recent Greenland mass loss. However, previous studies mainly focused on the extent and persistence of surface melt. The variations in surface melt rates and extreme events have not been adequately known, especially the role of extremes in the long-term surface melt changes. Here, using two high-resolution regional climate models (RACMO2.3p2 and MARv3.14), we analyzed the variations in Greenland surface melt in 1958–2023. Both models (RACMO/MAR) show that annual surface melt is rapidly increasing post-1990 at a rate of 8.6 ± 4.9/7.2 ± 4.4 Gt per year. The northern regions show the strongest relative regional increase rate (3.9% ± 1.9%/3.4% ± 1.6% per year), contributing more surface melt to the whole Greenland. Based on the 90th percentile of the daily distribution, we found that extreme surface melt events from May to September (M−S) have become more frequent post-1990 (0.7/0.8 ± 0.5 d per year). Compared with 1958–1990, M−S surface melt from extreme events has increased by 134/105 Gt per year and dominates the increase in the total surface melt. During extreme surface melt events, we found an increase in downward longwave radiation, net shortwave radiation and sensible heat flux. The rise in surface melt and extreme events post-1990 is linked to more frequent atmospheric blocking. This study improves our understanding of the role in ice sheet mass balance played by long-term variations in ice sheet surface melt and extreme events.