Vertical Structure of Diurnal Englacial Hydrology Cycle at Helheim Glacier, East Greenland

The interior dynamics of Helheim Glacier were monitored using an autonomous phase-sensitive radio-echo sounder (ApRES) during two consecutive summers. The return signals from all observational sites exhibited strong non-tidal, depth-dependent diurnal variations. We show that these variations in the glacier interior can be explained by an englacial diurnal meltwater cycle: a data interpretation that assumes constant ice-column composition through time leads to dynamical inconsistencies with concurrent observations from GPS and terrestrial radar. The observed diurnal meltwater cycle is spatially variable, both between different sites and in the vertical, consistent with the existence of a dense and complex englacial hydrologic network. Future applications of this observational technique could reveal long-term meltwater behavior inside glaciers and ice sheets, leading to an improved understanding of the spatiotemporal evolution of the basal boundary conditions needed to simulate them realistically.