ν B = 9.02 +217.09/T 2 + 528.48σ B
increasing ice floe thickness as re-
r 2 = 0.996
vealed in Figure 2 affects all other ice
S D = 0.98
properties. It turns out that this ef-
70
fect is favorable to the remote sound-
60
ing of sea ice. For example, Kovacs
7‰
Salinity =
and Morey (1991) and Kovacs et al.
50
(1996) have shown that a portable
40
electromagnetic induction sounding
system can be used to measure re-
30
motely an apparent bulk conductivity
20
from which an estimate of winter
4‰
Beaufort Sea ice thickness can be
0.08
4
made (Fig. 7). When the νB vs. σB at
0.06 0.04
8
12
σ B , Bulk D
0.02
16
0
re (C)
20
C Conduc
T, Temperatu
DC values listed in Tables 1 and 2
tivity (S/m
)
and from 20 other ice floes were com-
0.10
pared, it was found that the calcu-
70
lated bulk conductivity of Beaufort
0.08
Sea ice was directly related to νB, as
60
shown in Figure 8. Therefore, in prin-
0.06
ciple, it should be possible to esti-
50
mate both undeformed winter Arctic
Salinity = 7‰
0.04
ice floe thickness and bulk brine vol-
40
ume remotely using a conductivity
0.02
measurement system. Before the lat-
30
ter is possible, the relation between
0
the field- measured apparent bulk
20
4‰
conductivity, which is highly affect-
ed by the underlying seawater, and
10
the bulk brine volume of sea ice floes
20
16
12
8
4
T, Temperature (C)
of various thicknesses will need to
be determined. Conductivity mea-
Figure 6. 3-D presentation of sea-ice brine volume vs. DC conductiv-
surement at a frequency well above
ity and temperature with salinity as a parameter for an ice density of
0.911 Mg/m3 (a) and a boresight view from the above temperature
50 kHz is likely to be necessary to
separate the sea-ice conductivity con-
window (b).
sheet was determined along with its brine
0.8
volume νB vs. ice temperature and salinity.
An ice sheet bulk density of 0.911 Mg/m3
was used in the determinations. The calcu-
lated results are graphically shown in Figure
0.6
6. There is a decrease in brine volume with
decreasing ice temperature. In addition to
ice conductivity, Figure 6 indicates that ei-
0.4
ther ice salinity or temperature is required to
estimate νΒ.
The complex interrelationship between the
model sea-ice temperature, salinity, brine vol-
0.2
ume, and conductivity is well revealed in
Figure 6. The results suggest that determin-
ing σB of natural sea ice remotely will not, of
itself, allow νB to be estimated. Not revealed
0
2
4
6
8
Drill-hole-Measured Snow and Ice Thickness (m)
is the effect of density, which was fixed at
0.911 Mg/m3 for this example. The decrease
Figure 7. EM-31 instrument conductivity reading at ~10 kHz
in the bulk density and conductivity with
vs. ice floe snow plus ice thickness (from Kovacs et al. 1996).
5
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