| Summary: | Sliding velocity of glaciers is influenced by water pressure at the bed. Subglacial hydrology models are helpful for gaining insight into basal conditions, but models depend on several unconstrained physical parameters, and reproducing elevated water pressures in winter has been a challenge. We eliminate terms in the SHAKTI model that rely on uncertain parameters and apply this model to Helheim Glacier in east Greenland to explore the winter base state of the subglacial drainage system in the absence of meltwater inputs from the surface. Our results suggest that meltwater produced at the bed alone can support an active winter drainage system at Helheim. We produce large areas of elevated water pressure and naturally emerging preferential drainage pathways, with a continuum approach that allows for transitions between flow regimes and drainage system opening by melt. Transmissivity varies spatially over several orders of magnitude, including large regions of weak transmissivity, representing poorly connected regions of the system. Deeply incised bed topography controls the location of primary drainage pathways, with high basal melt rates along the steep walls. We examine the influence of frictional heat from sliding by comparing simulations with three different approaches for calculating basal shear stress.
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