The cooling signature of basal crevasses in a hard-bedded region of the Greenland Ice Sheet

Abstract. Temperature sensors installed in a grid of nine full-depth boreholes drilled the southwestern ablation zone Greenland Ice Sheet recorded cooling discrete sections ice over time within lowest third column most boreholes. Rates temperature change outpace expected from vertical conduction alone. Additionally, observed profiles deviate significantly site-average thermal profile that is shaped by all thermomechanical processes upstream. These deviations imply recent, localized changes to basal state Although numerous heat sources exist add energy and warm as it moves central divide towards margin such strain internal deformation, latent refreezing meltwater, geothermal across ice–bedrock interface, identifying sinks proves more difficult. After eliminating possible mechanisms could cause cooling, we find manifestation previous warming near-basal ice. Thermal decay after released freezing water crevasses likely mechanism resulting transient evolution structure at our site. We argue are viable englacial source Greenland's may have controlling influence on