Abstract
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.