water has a higher salinity than in the southern
6
Beaufort Sea. Therefore, the Antarctic sea ice
2
S B = 1.80 + 99810.49/TF
could have a higher salinity due to this pos-
r 2 = 0.438
sible exchange, if all other parameters are the
Arctic
same.
Antarctic
4
When multiyear sea ice SB vs. TF data
from Fram Strait (Gow et al. 1987) are added,
the distribution changes again, as shown in
Figure 22. The scatter in the data between 200
and 300 cm also increases. Some of the lower
2
salinity values from Fram Strait could have
resulted from sampling lower-salinity melt-pool
ice. Whatever the reason for the lower SB val-
ues, Figure 22 does indicate that sea ice that
0
has survived one or more melt seasons can
200
400
600
800
freshen to where the bulk salinity is 1 to 2‰.
T F , Floe Thickness (cm)
Figure 21. Beaufort Sea and Antarctic multiyear sea-ice
bulk salinity vs. floe thickness.
SUMMARY
Sea ice salinity data collected in Arctic and
2
Antarctic waters indicate that the bulk ice-sheet
6
S B = 1.85 +
80217.97/TF
salinity decreases with increasing ice floe thick-
r 2 = 0.222
ness following a negative exponential-like
trend. New ice about 0.05 m thick has a bulk
salinity of about 25‰. The bulk salinity of the
4
ice decreases rapidly to about 6‰ at an ice
thickness of about 0.5 m. After this, the bulk ice
salinity continues to decrease, but at a highly
reduced rate, to about 5‰ at the end of the
2
growth season for ice more than 1.5 m thick.
Reasons for the salinity decrease are related to
ice structure, rate of ice growth, and brine mi-
gration processes. The first and second reasons
0
200
400
600
800
are related, in that as the ice thickness increases,
T F , Floe Thickness (cm)
bulk the growth rate slows because the heat ex-
Figure 22. All Arctic and Antarctic multiyear sea-ice
change from the ice bottom to the atmosphere
salinity vs. floe thickness data.
is reduced. Slower growth results in the forma-
tion of larger freshwater ice platelets and larger
al. (1973), Cox and Weeks (1974), Kovacs (data on
ice crystals with proportionately fewer brine in-
file), and Meese (1989) are shown in Figure 20.
clusions. Thus, the ice salinity is lower. Brine mi-
The obvious trend is to lower SB values with in-
gration processes lead to the gradual drainage of
creasing ice thickness.
brine from the ice to the sea and a freshening of
When the higher SB vs. TF data for Antarctic
the ice.
multiyear ice (Gow et al. 1987) are added to the
Significant scatter and a paucity of data pre-
Beaufort Sea data the curve through the com-
cluded establishing a definitive relationship be-
bined data shifts up slightly for the thicker ice
tween seawater salinity and ice sheet structure
(Fig. 21). The higher Antarctic SB values may be
and the bulk salinity of the sea ice.
due to ice structure, thermodynamic differences
A significant decrease in ice floe bulk salinity
during the melt season, or differences in seawater
occurs during the melt season. Depending on
salinity. When the denser brine drains out of the
many factors, including the solar intensity during
sea ice during the melt season, some of the drain-
the melt season, the bulk salinity of a first-year
age system can be reoccupied by seawater (Nied-
sea-ice floe can decrease from about 5‰ to about
rauer and Martin 1979). In the Antarctic, the sea-
2‰. This transition to second-year ice separates
12
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