Seasonal drainage of ponded crevasses in response to dynamics at Greenlandic outlet glaciers

Greenland’s crevasses are responsible for transferring the majority of seasonal runoff to the bed of the ice sheet in fast-flowing regions, with implications for ice rheology, subglacial hydrology, and ice dynamic feedbacks. However, their drainage mechanics are poorly understood, particularly relative to other transfer mechanisms such as lake drainage and moulins. Here, we use remote-sensing products to identify relationships between strain rates and crevasse drainage at Greenland’s fast-flowing outlet glaciers. We map the time-series evolution of water-filled crevasses by training and applying a convolutional neural network (CNN) to 10 metre resolution Sentinel-2 MSI imagery, and extract contemporaneous logarithmic strain rates from NASA MEaSUREs ITS_LIVE velocity data. We test the time-evolving relationship between strain rates and crevasse ponding across a range of outlet glaciers, and examine whether significant relationships between the two processes can be detected. We find that crevasse drainage displays a unique response to seasonal strain rate evolution not detectable in analogous lake drainage studies, with drainage events occurring following a seasonal transition from compressive to tensile strain rate regimes. We aim to use these relationships to parameterise dynamic controls on crevasse drainage into coupled models of Greenland Ice Sheet hydrology-dynamics.