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

• Published in: Journal of Glaciology
• Main Authors: Doyle, Samuel H., Hubbard, Bryn, Christoffersen, Poul, Law, Robert, Hewitt, Duncan R., Neufeld, Jerome A., Schoonman, Charlotte M., Chudley, Thomas R., Bougamont, Marion
• Other Authors: Natural Environment Research Council, H2020 European Research Council
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 2021
• Subjects: Earth-Surface Processes; Greenland; Kujalleq; glacier; greenlandic; Journal of Glaciology; Sermeq Kujalleq
• Online Access: http://dx.doi.org/10.1017/jog.2021.121; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143021001210

Abstract 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.