Geoscience Reference
In-Depth Information
Table 3.2
Physical properties of freshwater lake ice at 0
°
C and
−
20
°
C temperature
Property
Value at 0
°
C Value at
−
20
°
C
Liquid water at 0
°
C
Density (kg m
−
3
)
916.7
920.3
999.8
Latent heat of melting (kJ kg
−
1
)
(333.5)
a
333.5
Latent heat of sublimation
(MJ kg
−
1
)
2.82
2.84
Latent heat of evaporation
(MJ kg
−
1
)
2.49
Specific heat (kJ kg
−
1
°
C
−
1
)
2.11
1.96
4.22
Thermal conductivity (W m
−
1
°
C
−
1
)
2.14
1.88
0.561
Young
'
s modulus (GPa)
8.7
10.0
Poisson
'
s ratio
0.33
0.33
Speed of sound (km s
−
1
)
3.08
3.30
1.45
Relative permittivity
91.6
97.5
87.90
a
Melting takes place only at 0
°
C
of saline ice, there are liquid brine inclusions within the ice sheet, and then the salt content
together with the temperature become the dominant factors. Congelation ice with columnar
crystals possesses anisotropy due to the geometry of ice crystals and alignment of c-axes.
Lake ice normally contains impurities, which in
uence its properties. In freshwater
ice, the primary impurity is gas bubbles, which cover a volume of magnitude 1 % in
congelation ice and 5 % in snow-ice. Lake ice also contains particles, which are in general
called ice sediments. In brackish and saline lakes, the brine content of ice is the primary
factor. Depending on the salinity of the parent water, liquid brine is captured by growing
ice, and brine pockets are formed within the ice sheet (see Weeks 2010).
fl
Example 3.3. The density of natural freshwater lake ice can be expressed as
q
i
¼ 1
m
a
ð
Þq
0
where
ρ
0
is the density of pure ice. This equation can be used to
estimate the gas content from the measured ice density. When
m
a
¼ 1
%
ʽ
a
is the gas content and
, then (at 0
°
C)
ρ
i
= 907.5 kg m
−
3
. Considering
m
a
1
%
as the scale in congelation ice, 910 kg m
−
3
serves as a convenient reference density.
3.2
Lake Ice Types and Stratigraphy
3.2.1 Ice Structure Analysis
Research on the crystal structure of ice is based on ice samples, which are usually taken by
core drills with diameter 10
20 cm. Not much can be said about the ice structure without a
manual sample processing. Ice samples are examined at the site for their visual features
-
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