Water flow through sediments and at the ice-sediment interface beneath Sermeq Kujalleq (Store Glacier), Greenland

• Published in: Journal of Glaciology
• Main Authors: Samuel H. Doyle, Bryn Hubbard, Poul Christoffersen, Robert Law, Duncan R. Hewitt, Jerome A. Neufeld, Charlotte M. Schoonman, Thomas R. Chudley, Marion Bougamont
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press 2022
• Subjects: Environmental sciences; GE1-350; Meteorology. Climatology; QC851-999; Greenland; Kujalleq; glacier; greenlandic; Journal of Glaciology; Sermeq Kujalleq
• Online Access: https://doi.org/10.1017/jog.2021.121; https://doaj.org/article/b42d1c1436d1446fa38ba96388fa36a5

Subglacial hydrology modulates basal motion but remains poorly constrained, particularly for soft-bedded Greenlandic outlet glaciers. Here, we report detailed measurements of the response of subglacial water pressure to the connection and drainage of adjacent water-filled boreholes drilled through kilometre-thick ice on Sermeq Kujalleq (Store Glacier). These measurements provide evidence for gap opening at the ice-sediment interface, Darcian flow through the sediment layer, and the forcing of water pressure in hydraulically-isolated cavities by stress transfer. We observed a small pressure drop followed by a large pressure rise in response to the connection of an adjacent borehole, consistent with the propagation of a flexural wave within the ice and underlying deformable sediment. We interpret the delayed pressure rise as evidence of no pre-existing conduit and the progressive decrease in hydraulic transmissivity as the closure of a narrow (< 1.5 mm) gap opened at the ice-sediment interface, and a reversion to Darcian flow through the sediment layer with a hydraulic conductivity of ≤ 10−6 m s−1. We suggest that gap opening at the ice-sediment interface deserves further attention as it will occur naturally in response to the rapid pressurisation of water at the bed.