Structural controls on the hydrology of crevasses on the Greenland ice sheet

Surface crevasses on the Greenland Ice Sheet deliver significant volumes of meltwater to the englacial and subglacial environment, but the topic has received little attention compared to supraglacial lake and moulin drainage. Here, we explore relationships between crevasse hydrology and the surface stress regime at a fast-flowing, marine-terminating sector of the Greenland ice sheet. Regional-scale observations of surface water, crevasses, and stress were made across a 3,000 km2 region using satellite data. Contemporaneous high spatio-temporal resolution observations were obtained from uncrewed aerial vehicle surveys on Store Glacier using a supervised classifier and feature-tracked velocities. While previous studies have identified crevasses using von Mises stress thresholds, we find these are insufficient for predicting crevasse hydrology. We found that dry crevasse fields, where no ponded meltwater was observed through the entire melt season, were more likely to exist in tensile mean stress regimes, which we interpret to be due to meltwater draining continuously into the englacial system. Conversely, wet crevasse fields, hosting ponded meltwater, were more likely to exist in compressive mean stress regimes, which we interpret to be a result of closed englacial conduits. We show that these ponded crevasses drain through episodic rapid drainage events (i.e. hydrofracture). Mean stress regime can therefore inform spatially heterogeneous styles of meltwater delivery through crevasses to the bed of ice sheets, with distinct consequences for basal processes such as subglacial drainage efficiency and cryo-hydrologic warming. Thus, we recommend simple guidelines for improving the representation of crevasse hydrology in regional hydrological models