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

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Authors

Samuel Huckerby Doyle, Bryn Hubbard , Poul Christoffersen, Robert Law , Duncan Hewitt , Jerome Neufeld , Charlotte Schoonman , Tom Chudley , Marion Bougamont 

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 elastic gap opening at the ice-sediment interface, Darcian flow through the sediment layer, and the forcing of water pressure in hydraulically-isolated cavities by elastic 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. 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.

DOI

https://doi.org/10.31223/X56W54

Subjects

Earth Sciences, Glaciology

Keywords

Subglacial sediments, Subglacial processes, Glacial tills, Ice dynamics, Subglacial sediments, Subglacial processes, Glacial tills

Dates

Published: 2021-07-05 10:48

Last Updated: 2021-07-05 17:48

License

CC BY Attribution 4.0 International

Additional Metadata

Data Availability (Reason not available):
Data will be deposited in a data repository at final publication.

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