A Critical Review of the Low-Frequency Electrical Properties of Ice Sheets and Glaciers

Abstract

I review current understanding of the low-frequency electrical properties of glaciers and ice sheets, and identify future research directions that challenge near-surface geophysicists and glaciologists. In cold ice electrical conduction occurs principally via [a] movement of protonic point defects in the lattice in low-impurity ice; [b] networks of impurities at grain boundaries in ice of moderate impurity content; and [c] triple junctions and grain boundaries in ice of high impurity content. I infer that in temperate ice Archie-type conduction is likely dominant. Arrhenius and Looyenga type models, respectively, describe well the increase in bulk resistivity with decreasing ice temperature and density. The activation energy in cold ice and firn is constant at ,0.25 eV but poorly constrained in temperate ice and snow. The bulk resistivity of cold ice ranges from ,0.4 3 10 5 Vm at 22uC to 4 3 10 5 Vm at 258uC, and is much higher in temperate ice (up to .1,000 3 10 5 Vm). The effects of impurity characteristics, temperature, and density on complex conductivity are poorly understood, although selected real conductivity components apparently increase with frequency, impurity concentration, or temperature. Future research should exploit more rigorously low-frequency electrical techniques in the field and laboratory, and develop or adapt from other areas of electrical geophysics novel mathematical and statistical concepts for joint data inversion and integration, for glaciological purposes such as ice core logging and investigations of glacier dynamics, ice fracturing, and glacier hydrology. I conclude that low-frequency electrical techniques have unduly been neglected in glaciology as compared with higher-frequency radar techniques over the past few decades, suggesting opportunities for concerted research efforts into these techniques.

Antarctic subglacial groundwater: a concept paper on its measurement and potential influence on ice flow

“…7a). Beneath the BIR, we introduced a hypothetical layer of permafrost, some 500 m thick with a resistivity intermediate between that of the ice sheet and the unfrozen groundwater-bearing sedimentary rock (French et al 2006;Kulessa 2007;Mikucki et al 2015;Foley et al 2016), under the assumption that basal freezing caused the major reorganization of the region's ice flow possibly as recently as 400 years ago (Siegert et al 2013). We then inverted synthetic MT data acquired at 40 simulated measurement stations along the profile line (Fig.…”

“…7b). In practice, glaciological MT data can be acquired with commercial off-the-shelf systems, although capacitive coupling of electrodes with highly resistive firn (Kulessa 2007 and references therein) must be boosted by high-input impedance buffer amplifiers that would normally be custom designed (Wannamaker et al 2004).…”

Anatomy of terminal moraine segments and implied lake stability on Ngozumpa Glacier, Nepal, from electrical resistivity tomography (ERT)

“…Despite significant uncertainty in the actual electrical conduction mechanism, the resistivity signature of glacier ice at Ngozumpa Glacier is a magnitude lower than values typically recorded for temperate glacial ice31486465. Very little is known about the thermal regime of large Himalayan debris-covered glaciers.…”

Geometry and drainage of a retreating glacier overlying and recharging a karst aquifer, Tsanfleuron-Sanetsch, Swiss Alps

“…Four frequencies were used, 234, 183, 77.5 and 19.6 kHz. As ice resistivity critically depends on meltwater saturation and consequently varies wit� temperature, t�e investigation dept� is also variable (Kulessa 2007). A two-layer model was used for t�e data inversion: glacier ice overlying limestone, w�ere ice t�ickness (Z), ice resistivity (ρ 1 ), and limestone resistivity (ρ 2 ) are t�e t�ree fit parameters (Fig.…”