1Aesir Consulting LLC, Missoula, Montana 59801, USA
2Department of Geosciences, University of Montana, Missoula, Montana
3Department of Geology and Geophysics, University of Wyoming, Laramie,
Wyoming 82071, USA
Received: 06 Sep 2016 – Discussion started: 30 Sep 2016
Abstract. Liquid water content (wetness) within glacier ice is known to strongly control ice viscosity and ice deformation processes. Little is known about wetness of ice on the outer flanks of the Greenland Ice Sheet, where a temperate layer of basal ice exists. This study integrates borehole and radar surveys collected in June 2012 to provide direct estimates of englacial ice wetness in the ablation zone of western Greenland. We estimate electromagnetic propagation velocity of the ice body by inverting reflection travel times from radar data. Our inversion is constrained by ice thickness measured in boreholes and by positioning of a temperate–cold ice boundary identified in boreholes. Electromagnetic propagation velocities are consistent with a depth-averaged wetness of ∼ 0.5–1.1 %. The inversion indicates that wetness within the ice varies from < 0.1 % in an upper cold layer to ∼ 2.9–4.6 % in a 130–150 m thick temperate layer located above the glacier bed. Such high wetness should yield high rates of shear strain, which need to be accounted for in glacial flow models that focus on the ablation zone of Greenland. This high wetness also needs to be accounted for when determining ice thickness from radar measurements.
Revised: 13 Jan 2017 – Accepted: 02 Feb 2017 – Published: 02 Mar 2017
Brown, J., Harper, J., and Humphrey, N.: Liquid water content in ice estimated through a full-depth ground radar profile and borehole measurements in western Greenland, The Cryosphere, 11, 669-679, doi:10.5194/tc-11-669-2017, 2017.