Among the most pressing consequences of recent climate warming is the acceleration of mass loss from the Greenland Ice Sheet (GrIS) since the late 1990s. GrIS mass loss contributes directly to global mean sea level rise and affects many other components of the global ocean-atmosphere-cryosphere system, including oceanic and atmospheric circulation and oceanic primary productivity. Several episodes of widespread GrIS surface melt in recent years have coincided with intense poleward water vapor transport in narrow plumes called atmospheric rivers (ARs), suggesting that these events play an important role in high-latitude warming. Climate model projections indicate that poleward moisture transport will intensify as a consequence of anthropogenic climate change. In this dissertation, the impact of poleward moisture transport by ARs on the GrIS is comprehensively assessed from a local- to planetary-scale energy and mass balance perspective. Impacts of ARs on GrIS surface mass balance (SMB) on daily, seasonal, and annual time scales are first examined. Strong summer ARs are found to cause intense melt events in western Greenland, and an increasing trend in AR-related moisture transport is found to correspond with the recent increase in GrIS mass loss. The physical mechanisms by which ARs force GrIS melt are analyzed in the second part of this work through examination of changes to the surface energy balance and cloud properties induced by AR events. ARs are found to provide melt energy through multi-scale, spatially variable surface-atmosphere interactions, with ice sheet surface melt produced in cloudy, windy conditions in the area of AR landfall and in clear-sky downsloping flow in areas separated from the AR landfall by the topographic barrier of the ice sheet. The third part investigates the dynamical processes by which ARs link distant regions within the global hydrological cycle, through identification of the evaporative water vapor source regions and moisture transport processes that produce AR events in western Greenland. Moisture fluxes during ARs originate from lower-latitude evaporative sources compared to typical conditions, with enhanced moisture uptake occurring over a broad swath of the Atlantic Ocean during summer and winter, as well as northeastern North America during summer.