Figure 6. On surface EMI conductivity measurement vs. drill hole measured snow plus ice thickness

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Figure 6. On surface EMI conductivity measurement vs. drill hole measured

snow plus ice thickness.

Figure 7. Comparison of the EMI snow and ice thickness measurements made

parallel vs. perpendicular to the survey line.

and Morey 1978, 1979; Morey et al. 1984) and

side between the vertical basal plane of the nu-

mechanical (Payton 1966, Wang 1979, Timco and

merous fresh ice platelets that make up the sea ice

Frederking 1990, Kovacs 1993) properties of the

crystal structure as depicted (Fig. 8). When the c-

ice.

axes of the ice crystals are all aligned, then the

The bottommost 0.2-m portion of the ice sheet

brine inclusions reside in parallel rows. Radar

causes the largest change in the sea ice electro-

reflection measurement has shown that when the

magnetic properties. Here the entrapped brine,

antenna E-field is aligned parallel with the pre-

which governs the ice conductivity, increases ex-

ferred horizontal c-axis direction of the ice crys-

ponentially with depth. The brine inclusions re-

tals at the bottom of the ice sheet, maximum re-