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

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.

This value can now be used in eq 3 or 4 to

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

The equation for predicting the bulk brine vol-

* Sea-ice conductivity is approximately constant between DC

ume νB in ‰ as a function of *S*B and the absolute

and 100 MHz (see Tables 1 and 2).

value of *T*A (Fig. 4),

30

ν B = 41.64 *S*B.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 *T*F (cm)

(Fig. 5),

(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)

ν 0.5.

σt = 0.816 - 0.069

(3)

B

4