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with depth. This is confirmed in measurements on
natural sea ice by Tabata and Ono [1962] as well as Weeks
and  Hamilton [1962]. Gow and Weeks [1977] observed
fluctuations of brine spacing that decrease toward the
bottom of the ice sheet. However, they found it difficult
to explain the fluctuations in brine spacing because of
the limited data available on the growth history of sea ice
they examined. In fact, the difficulty in obtaining the
complete growth history of sea ice at a given location was
the main reason for the lack of meaningful data on brine
layer spacing in the pre‐1984 literature.
The first systematic analysis of brine layer spacing in
FY sea ice with full knowledge on the detailed growth his-
tory of ice, described in Sinha and Nakawo [1981] and
Nakawo and Sinha [1981], was accomplished by Nakawo
and Sinha [1984]. They conducted their measurements on
ice core samples taken from the Eclipse Sound near Pond
Inlet on Baffin Island, Canada, in January 1978. Using a
record of daily mean air temperature, histories on snow
and ice thickness, and appropriate physical constants for
snow and ice, the authors estimated the growth rate of sea
ice of a given thickness using equation (2.17) (see sec-
tion  2.2.4.1 on modeling ice growth). The calculated
growth rate for one of the cores is plotted against ice depth
as shown in Figure  4.50. The running average of the
growth rate would be more realistic because the thermal
resistance of the snow‐ice system dampens the variations
in daily air temperature and therefore the growth rate. The
figure shows three maxima of ice growth rate at about 0.2,
0.5, and 1.0 m. The authors found that they correspond to
cold periods in November, December (1977), and January
(1978). The small growth rate at about 0.8 m corresponds
to the warm period in late December between the latter
two cold periods. The similarity between the running
average of the growth rate and the salinity profile (middle
graph in Figure  4.50) is an indication of the correlation
between the two parameters. Brine spacing was measured
manually from photographs of thin sections. Figure 4.50
shows also the relation between growth rate and brine
spacing; a large growth rate seems to give a small spacing,
and vice versa. This general tendency agrees with previous
observations as mentioned above. The data on the bottom
two sections, however, are not compatible with this gen-
eral trend. The growth rate decreased with depth near the
bottom, yet the brine layer spacing also decreased sharply.
The same data from Figure  4.50 are plotted in
Figure 4.51 to show the relation between the brine layer
spacing and the ice growth rate. The spacing tends to be
inversely proportional to growth rate (the broken line in
the figure), in accordance with the theoretical results by
Bolling and Tiller [1960] and laboratory studies [ Rohatgi
and Adams, 1967; Lofgren and Weeks, 1969]. The two
anomaly points in Figure 4.51 reflect the anomaly shown
in Figure  4.50 when the brine layer spacing decreases
while the ice growth rate also decreases near the bottom
of the core. Nakawo and Sinha [1984] found that brine
spacing depends on crystallographic orientation, which
was not taken into account in the results presented in
Figure 4.50. They suggested that this might be the cause
for the anomalies. In general, the correlation between
brine layer spacing and ice growth rate provides a record
of the conditions, especially weather, under which ice is
formed. Jefferies et al. [1993] found similarities in the
measured brine spacing in ice from the Arctic and the
Antarctic so he concluded that fast‐ice growth rates are
similar in the two polar regions.
0
0.05
0.10
0.15
0.20
0
0.2
0.4
c
0.6
b
0.8
a
1. 0
Bottom
1. 2
0
1. 0
Growth rate (cm/day)
0.5
1. 5
2.0 468 0
12 0.2
0.4
0.6
0.8
1. 0 .2
1. 4
Salinity (‰)
Brine layer spacing (mm)
Figure 4.50 Profiles of growth rate, salinity, and brine layer spacing from a FY ice core obtained in Eclipse Sound,
Canadian Arctic, in January 1978. The ice thickness was 1.17 m. Curve b represents the running mean of calcu-
lated growth rate (curve a ), for an interval of ± 50 mm for every 25 mm. The average ice growth rate was 8.5 cm/
day [ Nakawo and Sinha, 1984].
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