tribution. A dual high and low frequency

0.74

νB = 584 σ

100

B

r 2 = 0.984

system or a wideband measurement system

S D = 3.169

could be used.

80

In the interim, an off-the-shelf electromag-

netic induction system operating at 10 kHz

60

can be used to estimate ice thickness (Fig. 8),

and the bulk salinity of the ice is estimated

using eq 2. After determining the average ice

40

sheet temperature, as previously described,

eq 1 can be used to calculate the bulk brine

20

volume. Ice strength may then be calculated

from eq 3 or 4.

The relation between sea-ice tensile or flex-

0

0.02

0.04

0.06

0.08

0.10

ural strength, brine volume, and the calcu-

σB , Bulk DC Conductivity (S/m)

lated bulk DC conductivity of natural sea ice

is shown in Figures 9 and 10. These figures

are the result of using the equation in Figure

6 and eq 3 and 4, respectively. In the future,

using similar equations, an algorithm

could be added to a portable electro-

magnetic induction sounding system

0.8

that would provide both ice thickness

and strength from the apparent sea-ice

0.8

0.6

conductivity measurements.

0.6

0.4

0.4

0.2

0.2

0

Estimating the compressive strength

100

‰)

e(

75

of sea ice is different. While the uniaxial

0

m

olu

50

eV

2

0.0

tensile or flexural strength of sea ice

.04

rin

25

.06

B

σ B, Bulk 0

ulk

.08

0

DC Con 0

does not reveal a significant strain rate

0

,B

ductivity 0

0.1

νB

(S/m)

dependence, at the strain rates of inter-

est for most ice engineering problems,

the compressive strength does. In addi-

tion, in reporting sea-ice compression

test results, the recent, and correct,

method is to relate strength to total po-

rosity: brine volume plus gas volume.

1.0

Recently, Timco and Frederking (1990)

1.0

0.8

developed empirical equations for pre-

0.8

dicting the large-scale uniaxial uncon-

0.6

fined compressive strength of Arctic sea

0.6

0.4

ice. Their equations are based on small-

0.4

scale strength tests and the various con-

0.2

trolling factors, such as ice structure,

0.2

0

brine volume, porosity, loading direc-

100

‰)

(

80

me

0

tion (horizontalvertical), and strain

60

olu

eV

40

2

0.0

n

4

Bri

rate. Their strength equation for hori-

20

0.0

6

0.0

σ B, Bulk

ulk

8

0

0.0

0

B

0.1

ν B,

DC Con

zontally loaded columnar sea ice is

ductivity

(S/m)

[

],

σc = 37 ε0.22 1 - (φB / 270)

0.5

˙

(5)

6