Atmospheric Blocking Pattern as the Primary Driver of Subseasonal Greenland Ice Sheet Summer Melt Variability

ABSTRACT

The anomalous summer melting of the Greenland Ice Sheet (GrIS) is one of the key signals of ongoing climate system changes. The complex spatiotemporal characteristics of GrIS and its impacts on global sea‐level rise have attracted increasing attention. Although previous studies have suggested that atmospheric blocking circulation can drive extreme melting events, the quantitative influence of subseasonal‐scale atmospheric processes on the total summer melt remains poorly understood. Based on a scale‐separation approach combined with Modèle Atmosphérique Regionale (MAR) simulations and satellite observations, this study provides the first systematic quantitative assessment of the contribution of subseasonal circulation processes to summer melting of the GrIS. While subseasonal processes account for an average of ~20% of the total summer melt, we find that a single pattern—Greenland Blocking (GB)—dominates this contribution. GB alone is responsible for up to 47% of the subseasonal melt, equating to approximately 10% of the total summer melt. The remaining subseasonal variance is driven by a spectrum of other circulation modes. To unravel the remaining subseasonal signal, we employ K‐means clustering to identify four distinct non‐blocking circulation patterns. However, their individual contributions are substantially smaller than that of GB. This study reframes the understanding of summer GrIS melt by highlighting the overwhelming dominance of blocking within the subseasonal framework.