Evaluation of Greenland extreme snow melting patterns and their synoptic drivers

 

Greenland Ice Sheet (GrIS) snow melting rates have drastically increased since the 1990s, with relevant implications in the entire ecosystem. According to climate projections, extreme weather events will potentially increase in the coming decades over the GrIS. Thus, it is necessary to analyze the past temporal evolution of GrIS extreme melting patterns, as well as their climate drivers. This work analyzes the GrIS summer extreme snow melting spatiotemporal evolution and trends (1990 to 2021). Further, we determine the contribution of synoptic weather types that drive extreme snow melting events. Results evidence that the frequency, magnitude, and the relative contribution of extreme snow melting to the total summer snow melting differs depending on the GrIS sector. Maximum extreme snow melting days per season are observed in western GrIS, whereas minimums are observed in northern sectors. The average extreme snow melting during summer is non-statistically significant increasing in the entire GrIS, which is consistent with the increase of the average snow melting for the same temporal period. Extreme snow melting days as well as the contribution of extreme snow melting to the total snow melting per season show an upward trend, except in the central and northern zones. The analysis of twenty summer circulation weather types reveals that extreme snow melting episodes for most of the GrIS sectors are mainly explained by a few synoptic systems; characterized by a high-pressure system located in central, southern, and eastern GrIS. During these synoptic episodes, stable weather conditions prevail, and the energy available for snow melting is mainly controlled by positive shortwave radiation heat fluxes leading to positive 850 hPa air temperature anomalies. Results presented in this work are relevant for a better understanding of extreme weather events over GrIS within a changing climate context.