A permeameter for temperate ice: first results on permeability sensitivity to grain size

• Published in: Journal of Glaciology
• Main Authors: Fowler, Jacob R., Iverson, Neal R.
• Other Authors: US National Science Foundation
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 2022
• Subjects: Journal of Glaciology
• Online Access: http://dx.doi.org/10.1017/jog.2021.136; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143021001362

Abstract Results of ice-stream models that treat temperate ice deformation as a two-phase flow are sensitive to the ice permeability. We have constructed and begun using a custom, falling-head permeameter for measuring the permeability of temperate, polycrystalline ice. Chilled water is passed through an ice disk that is kept at the pressure-melting temperature while the rate of head decrease indicates the permeability. Fluorescein dye in the water allows water-vein geometry to be studied using fluorescence microscopy. Water flow over durations of seconds to hours is Darcian, and for grain diameter d increasing from 1.7 to 8.9 mm, average permeability decreases from 2 × 10 −12 to 4 × 10 −15 m 2 . In tests with dye on fine ( d = 2 mm) and coarse ( d = 7 mm) ice, average area-weighted vein radii are nearly equal, 41 and 34 μm, respectively. These average radii, if included in a theory slightly modified from Nye and Frank (1973), yield permeability values within a factor of 2.0 of best-fit values based on regression of the data. Permeability values depend on d −3.4 , rather than d −2 as predicted by models if vein radii are considered independent of d . In future experiments, the dependence of permeability on liquid water content will be measured.