Geology Reference
In-Depth Information
Table 2.3
Summary of parametric relationships for ridges of first‐year ice (first four rows) and multi‐year ice (last two rows);
n
is
the number of data points and
r
2
is the correlation coefficient [adapted with modifications from
Timco et al
., 2000].
a
b
95%
confidence
limit
95%
confidence
limit
Standard
deviation
Standard
deviation
Equation
n
r
2
Value
Value
97
0.793
4.60
0.31
4.00
0.88
0.79
0.79
b
H H
k
s
b
65
0.746
5.67
1.13
3.41
0.87
0.72
1.01
W H
k
k
b
75
0.713
30.75
1.98
16.81
0.78
0.65
0.90
W H
k
s
b
33
0.896
17.46
4.82
8.73
0.82
0.70
0.94
A A
k
s
H H
km
b
47
0.878
3.66
0.30
3.06
0.91
0.82
1.01
sm
A A
b
km
10
0.921
8.82
4.42
−1.42
1.00
0.76
1.24
sm
W
s
α
s
= 20.7° (temperate)
= 32.9° (Beaufort)
H
s
P
k
= 0.14 + 0.73 P
s
α
k
= 26.6°
H
k
W
k
H
k
/
H
s
= 4.4
W
k
/
H
s
= 15.1
A
k
/
A
s
= 8.0
W
k
/
H
k
= 3.9
Figure 2.50
Average ratios and relations between first‐year ice
ridge parameters based on the analysis of 112 ridges. Dashed
line is the sea level [after
Timco and Burden
, 1997].
Figure 2.51
A photograph of a rubble field of first‐year ice in
Resolute Passage, Canadian Arctic, taken in May 1991 (photo-
graphed by M. Shokr).
process when the two sheets have similar thickness even
if the thickness is not small (e.g., between 50 and 90 cm).
They also examined the effect of uneven thickness distri-
bution on the ridging/rafting processes. The simulations
showed that rafting predominates when each sheet has
uniform thickness and ridging predominates when the
sheets have an uneven thickness. It also showed varying
mixtures of rafting and ridging behaviour in a parame-
teric space of thickness and measure of the uniformity of
thickness distribution. In general, the thickness inhomo-
geneity of either one or the two sheets is an important
parameter that determines the likelihood of rafting or
ridging. Depending on the thickness of the two sheets
and homogeneity of the thickness distribution the result
of the collision of the two sheets varies from (1) simple
two‐layer rafting, (2) multiple layering rafting, (3) ridging
with some layering of rafting, or (4) pure ridging.
If the momentum of crushing continues between the
two ice sheets following the initial impact of collision,
deformation continues and a rubble field is formed.
Rubble ice is a wide accumulation of randomly dispersed
fragments or small ice pieces that cover a larger expanse
of area without any particular order as shown in
Figure 2.51. Rubble ice covers large areas in Antarctic ice
regime where the ocean swells break up newly forming ice
and herd it together into rubble ice fields.
As mentioned earlier, shear ridging develops when
shear force acts at the boundary between stationary (fast)
ice sheet and mobile ice. A shear ridge may also develop
locally between the boundary of a large floe and a highly
fragmented ice zone [
Kovacs
, 1970]. The ice in the shear
zone undergoes extensive crushing and consists of numer-
ous upturn blocks. Local shear ridges are frequently short
in length and straight in the plan view. Unlike pressure
ridges, shear ridges do not contribute to the ice thickness
redistribution, but they impact ice drift and deformation
of ice near the shores.
Large‐scale ice deformation of the order of 100 km and
more is triggered by equally large‐scale ice motion: a feature
