Similarly, ice floe flexural strength σf may
ν B = 41.64 SB.88 TA 0.67
0
be estimated using the empirical equation
r 2 = 0.995
(Timco and O'Brien 1994)
S D = 1.73
νB
σ f = 1.76 e 5.88
.
(4)
100
These expressions could be used as fol-
80
lows. Ice thickness is determined by drill-
hole measurement. Then from eq 2 the bulk
60
salinity of the ice is estimated. Ice tempera-
40
ture is determined next at 2025 cm below
the ice surface. A linear temperature gradi-
20
ent to the ice/water interface (~1.7C) is
8
0
6
assumed, and the average ice sheet tem-
10
(‰)
4
8
nity
perature is calculated. The bulk salinity and
Sali
2
6
T , Avg
ulk
. Floe T
A
4
,B
0
emp. (|
average temperature values are then used
SB
C|)
in eq 1 to determine the bulk brine volume.
Figure 4. Sea-ice bulk brine volume vs. average absolute ice
This value can now be used in eq 3 or 4 to
temperature and bulk salinity.
determine σt or σf, respectively. It should
be noted that Gavrilo et al. (1995) com-
vs. ice-sheet average temperature and bulk salin-
pared various published expressions for deter-
ity. It should be realized that Figure 3 is an end
mining the flexural strength of sea ice and found
view of the 3-D data presentation in Figure 4. In
that eq 4 gave σf values 2 to 4 times higher than
Figure 3, the points with no vertical tails are within
other research results. Further evaluation of the
one standard deviation (SD) of the brine volume
various σf equations may be in order.
surface shown in Figure 4. Points with tails lie
The above procedure still requires a drill-hole
between one and two standard deviations of the
thickness and a near-surface ice temperature mea-
brine volume surface, which is located at the tip
surement. These measurements may not be nec-
of the vertical line.
essary. Using the formulations for determining
the electromagnetic properties of sea ice (Kovacs
and Morey 1987), the low-frequency (DC to ~100
TENSILE AND
FLEXURAL STRENGTH
The equation for predicting the bulk brine vol-
* Sea-ice conductivity is approximately constant between DC
ume νB in ‰ as a function of SB and the absolute
and 100 MHz (see Tables 1 and 2).
value of TA (Fig. 4),
30
ν B = 41.64 SB.88 TA0.67 ,
0
(1)
SB = 4.606 + 91.603/TF
r 2 = 0.730
along with the expressions of Kovacs (1996)
S D = 1.47
for estimating the bulk salinity (‰) of first-
20
year sea ice vs. ice floe thickness TF (cm)
(Fig. 5),
SB = 4.606 + 91.603 /TF ,
(2)
10
offer the opportunity to make other ice prop-
erty assessments, which in turn can be used to
estimate ice sheet strength.
For example, the horizontal uniaxial tensile
strength σt of an ice sheet could be estimated
0
50
100
150
200
using the empirical equation of Dykins (1970):
TF , Floe Thickness (cm)
Figure 5. Combined Arctic and Antarctic ice floe bulk
ν 0.5.
σt = 0.816 - 0.069
(3)
salinity vs. thickness (from Kovacs 1996).
B
4
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