Long‐Term Support of an Active Subglacial Hydrologic System in Southeast Greenland by Firn Aquifers

The state of the subglacial hydrologic system, which can modify ice motion, is sensitive to the volume and rate of meltwater reaching it. Bare-ice regions rapidly transport meltwater to the bed via moulins, while in certain accumulation-zone regions, meltwater first flows through firn aquifers, which can introduce a substantial delay. We use a subglacial hydrological model forced with idealized meltwater input scenarios to test the effect of this delay on subglacial hydrology. We find that addition of firn-aquifer water to the subglacial system elevates the inland subglacial water pressure while reducing water pressure and enhancing subglacial channelization near the terminus. This effect dampens seasonal variations in subglacial water pressure and may explain regionally anomalous ice-velocity patterns observed in Southeast Greenland. As surface melt rates increase and firn aquifers expand inland, it is crucial to understand how inland drainage of meltwater affects the evolution of the subglacial hydrologic system.