Open AccessModeling the anisotropic brine microstructure in first‐year Arctic sea ice
Author(s) -
Jones K. A.,
Ingham M.,
Eicken H.
Publication year - 2012
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2011jc007607
Subject(s) - geology , brine , electrical resistivity and conductivity , anisotropy , porosity , arctic , thermal conduction , microstructure , permeability (electromagnetism) , materials science , mineralogy , geotechnical engineering , composite material , thermodynamics , optics , oceanography , physics , genetics , membrane , biology , electrical engineering , engineering
Cross‐borehole DC resistivity tomography has recently been used to monitor the temporal variation of the anisotropic bulk electrical resistivity of first‐year Arctic sea ice during the period of spring warming. These measurements cannot be explained by standard models of sea ice microstructure which treat the brine phase as isolated ellipsoidal pores. A simple structural model which does satisfy the observed electrical data shows that the brine phase must be connected both vertically and horizontally. Calculation of the temporal and thermal evolution of the microstructure suggests that although vertical connectivity is through pore tubes and sheets with widths of ∼100 μ m, horizontal connectivity is through much thinner connections which are interpreted as inter‐ and intragranular brine layers. As the temperature increases the width of vertical channels increases smoothly. In contrast, at temperatures above about −2°C there is a rapid increase in the thickness of horizontal connections which we interpret as a change from conduction through intergranular brine layers to the development of horizontal pores. The electrical data also broadly exhibit a percolation transition predicted by mathematical models. However, the critical brine volume fraction for vertical electrical connection is very small, while that for horizontal electrical connection is derived to be about 0.5%. The difference between these and the critical threshold of 5% for fluid permeability is presumed to arise because of the strong dependence of the latter on brine channel width.