The Anomalously Warm Summer of 2023 Over Greenland as Compared to Previous Record Melt Summers of 2012 and 2019

Abstract. Atmospheric circulation anomalies have increasingly contributed to extreme summer melt events over the Greenland ice sheet (GrIS). Based on our analysis of the visible and near-infrared top-of-atmosphere reflectance (R^TOA), we identified the summer of 2023 as another such instance comparable to the anomalously warm conditions observed in 2012 and 2019. Individual summer month and summer-wide R^TOA averages reveal that in 2023 the largest fraction of the GrIS experienced negative anomalies exceeding one standard deviation below the 2007–2024 mean, including the high-albedo central ice sheet. By incorporating higher-level satellite retrievals, in situ automatic weather station data, reanalysis, and regional climate model output, we disentangle the R^TOA signal to better assess the processes that preconditioned and led to the observed negative anomalies. We compare the extreme melt summers of 2012 and 2019 with 2023, to identify distinct pathways through which anticyclonic conditions contribute to GrIS surface melt. Our findings reveal that both dry (clear-sky) conditions, observed in 2019, and wet (cloudy) conditions, observed in 2012 and 2023, can trigger anomalous melting of the GrIS, with the primary difference being whether it is the margins or the central ice sheet that is most affected. Moreover, we find that both types of conditions are driven by atmospheric circulation patterns, shaped by the position, intensity, and persistence of anticyclones and the atmospheric rivers they help steer.