The anomalously warm summer of 2023 over Greenland as compared to previous record melt summers of 2012 and 2019

Abstract

The Greenland ice sheet (GrIS) is a major regulator of Earth’s climate and sea levels. Atmospheric circulation anomalies have increasingly contributed to extreme summer melt events over the GrIS. Based on our analysis of the visible and near-infrared top-of-atmosphere reflectance (RTOA), 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 combined June–July–August (JJA) RTOA averages reveal that in 2023 the largest fraction of the GrIS experienced negative RTOA 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 RTOA signal to better assess the processes that preconditioned and led to the observed negative RTOA 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 clear-sky conditions, observed in 2019, and 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. Furthermore, were it not for the colder-than-average June in 2023, our findings show that the total summer melt would likely have rivaled the extreme levels observed in 2012.