Geology Reference
In-Depth Information
10
10
Mean ice temperature
Bulk salinity
5
8
0
6
Top ice temperature
-5
4
-10
2
-15
0
-20
0.5
16
Snow thickness
14
0.0
12
10
-0.5
Ice thickness
8
-1.0
6
4
-1.5
2
σ
3 mm full thickness
in situ borehole strength
-2.0
140
0
150
160
170 180
Julian day
190
200
210
Figure 2.60
Relationship between physical property measurements and NRC-borehole indentation pressure,
σ
3mm
, corresponding to the indentation depth of 3mm, in FY ice during decay period [Johnston,
et al
. 2001].
Note:
σ
3mm
is significantly less than the “ultimate compressive strength” of ice that a floating structure will face during
interactions; it is only an index for comparison purposes.
when the pond water drains. They are commonly referred
to in the literature as “melt pond ice.” This term is used in
this topic as well. It is usually characterized by superim-
posed ice formed from pond or rain water. The water can
be mixed or even saturated with snow. The top layer of melt
pond ice is usually covered with snow ice (section 4.3.3).
The difference in salinity and density between FY ice
and MY ice has already been discussed in section 3.3. In
general, MY ice is much less saline and contains more
bubbles with considerably larger size than FY ice (sec-
tion 4.4.3). What remains to be addressed here is the dif-
ference between hummock ice and melt pond ice in terms
of salinity and air volume contents. The top surface of
hummock ice is less saline yet remarkably bubblier than
the top surface of pond ice. Field measurements pre-
sented in numerous studies by several authors have con-
firmed that the salinity of the top 0.2 m of MY ice
hummocks varies between 0 and 0.5‰, while that of melt
Figure 2.61
A photograph of part of what appeared to be
second‐year ice located in Parry Channel, Canadian central
Arctic, showing the undulating topography of the surface.
The snow cover ranged between 0.1 and 0.5 m. A few
hummocks are indicated by the arrows (photographed by
M. Shokr).
