Journal cover Journal topic
The Cryosphere An interactive open-access journal of the European Geosciences Union
The Cryosphere, 11, 669-679, 2017
https://doi.org/10.5194/tc-11-669-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
02 Mar 2017
Liquid water content in ice estimated through a full-depth ground radar profile and borehole measurements in western Greenland
Joel Brown1,2, Joel Harper2, and Neil Humphrey3 1Aesir Consulting LLC, Missoula, Montana 59801, USA
2Department of Geosciences, University of Montana, Missoula, Montana 59801, USA
3Department of Geology and Geophysics, University of Wyoming, Laramie, Wyoming 82071, USA
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.

Citation: 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, https://doi.org/10.5194/tc-11-669-2017, 2017.
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Short summary
We use ground-penetrating radar surveys in conjunction with borehole depth and temperature data to estimate the liquid water content (wetness) of glacial ice in the ablation zone of an outlet glacier on the western side of the Greenland Ice Sheet. Our results show that the wetness of a warm basal ice layer is approximately 2.9 % to 4.6 % in our study region. This high level of wetness requires special attention when modelling ice dynamics or estimating ice thickness in the region.
We use ground-penetrating radar surveys in conjunction with borehole depth and temperature data...
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