Year-Long Observations of Englacial and Subglacial Hydrology at Store Glacier from Autonomous Radar

Surface meltwater input into the Greenland Ice Sheet exerts a fundamental control on the dynamic motion of glaciers at its margins. Most of our current understanding of glacial hydrology is based on short-term field observations recorded during the spring and summertime. However, the wintertime subglacial hydrology condition may also play an important role in pre-conditioning the ice dynamic response in summer and early fall. Here we provide one of the few continuous year-long (July 2018 to June 2019) observations of englacial and subglacial hydrology at Store Glacier, West Greenland, gleaned from autonomous phase-sensitive radio echo sounding (ApRES) data. By tracking changes in englacial radar return power alongside surface conditions measured from an adjacent weather station, we are able to infer the response of temporal variations in meltwater storage within the ice column to supraglacial melt. While this englacial storage appears to be isolated from the subglacial hydrological system outside of the melt season, we observe its recovery from summer melt to be prolonged well into the winter. During an unusually warm spring, we observe rapid springtime meltwater percolation at Store Glacier, followed by a synchronous surface-to-bed connection coincident with more surface melting near the advent of the summer melt season. Together, these results not only support previous hypotheses of inherently leaky ice at Store Glacier, but also suggest a more hydrologically dynamic ice sheet across all seasons than previously assumed.