The seasonal evolution of subglacial hydrology exerts a primary control on ice sheet flow, yet the spatial structure and temporal evolution of subglacial drainage systems remains incompletely characterized. Here, we apply Sentinel-1 double-difference SAR interferometry across a land-terminating sector of the western Greenland Ice Sheet to resolve two distinct surface motion signals: (1) widespread late-summer flow deceleration followed by gradual recovery across an area extending ~110 km inland, and; (2) localized ice-surface subsidence, primarily aligned with bed troughs, persisting for several weeks after surface melt cessation. We interpret these signals as the dynamic response to coexisting subglacial drainage system components. The broad-scale flow speed recovery reflects progressive repressurization of the widespread weakly connected cavity system, driven by basal meltwater recharge. The trough-localized subsidence reflects a multi-week buffered release of stored water through well-connected corridors. Together, these signals provide a spatially-continuous view of the geometry and spatial extent of both the well- and weakly connected components of the late-season drainage system. Our findings highlight the disproportionate role of bed trough environments in late-season meltwater storage and drainage, demonstrate that the well-connected drainage system remains hydraulically active well beyond surface melt cessation, and emphasize the weakly connected system as the driver of large-scale seasonal ice flow changes.