A Recipe for Greenland snow events: Atmospheric Blocking and Moisture

Presently, the greatest contribution to global sea level rise is meltwater from the Greenland ice sheet (GrIS). This loss of mass is largely driven by surface mass balance processes, specially from net snow accumulation. As such, understanding what drives precipitation over the GrIS in the current climate is a key component in predicting changes to the GrIS in future climates. In this study we investigate and find a strong link between North Atlantic and European atmospheric blocking events and GrIS snowfall. Employing observations from the Integrated Characterization of Energy, Clouds, Atmospheric State and Precipitation at Summit (ICECAPS) suite of instruments at Summit Station, two main snowfall regimes are examined: snow events originating from entirely glaciated ice clouds (IC), and snow events associated with mixed-phase clouds, which have measurable column cloud liquid water (CLW). We present a "recipe" for IC and CLW snow events requiring two main ingredients: a moisture source such as transient cyclones, and a persistent large-scale circulation pattern associated with blocking.