Geology Reference
In-Depth Information
(a)
(b)
0
−0.2
−0.4
−0.6
−0.8
−1
−1.2
−1.4
−1.6
0
Freeboard
−0.2
−0.4
−0.6
−0.8
−1
−1.2
−1.4
−1.6
−1.8
Station 8
2
2
8
5
5
Station 2, 13 July
3
6A
Station 3, 13 July
Station 5, 13 July
3
Station 8, 13 July
2 ppt
salinity
marker
Station 6A, 13 July
Station 7
5
Station 7, 13 July
6A
Station 7
−1.8
0
5
10
15
20
25
30
0
2
4
Salinity, ppt
6
8
Salinity, ppt
Figure 5.14
Vertical salinity profiles in ice at (a) six sites across Mould Bay on 13 July 1982 and individual profiles
on the same day at six sites, using an expanded scale for salinity and (b) vertical broken line to represent a value
of 2 ppt (‰) given as a reference.
which also illustrates the concomitant reduction in the
thickness of ice.
The effect of melting and drainage, as can be visualized
from Figure 5.15, also caused the ice surface to become
undulated, forming hummocks, with a relief of about 0.3
m. These relatively low‐relief hummocks were long and
narrow with their long axis parallel to the long axis of the
channel and prevalent wind direction. Melting processes
led to the formation of shore leads along both east
and west coasts of the bay, but according to the notes
kept by the staff of the weather station, a large part of
this 1981-1982 ice cover remained relatively stationary in
the bay. Fortunately for the historians of sea ice research,
the ice sheet was not driven out of the bay into the Crozier
Channel by any wind or wave actions. However, the
details on the thickness distribution of this freely floating
ice at the end of the peak of summer melting in late
August 1982 could not be ascertained. Moreover, the
amount of ablation from the top and the erosion from
the bottom could not be established. Obviously, this
freely floating section, representing the middle part of the
annual ice sheet, probably grew during the middle of the
growth season of 1981-1982, perhaps during the growing
days of 100-150 (see Figure 5.8) corresponding to the
months of January and February 1982.
During the fall of 1982, the sections of the matured FY
ice cover that survived through the summer melting and
did not move away from the bay may be called the “rem-
nant 1GS” sea ice. 1GS is defined as the ice that has gone
through one growth season from the initial freeze‐up time
to the end of the first melting season or the beginning of
the second growth season (2GS). This remnant 1GS ice,
therefore, entered the life of its 2SG in September 1982.
With the advent of the winter in September 1982, the
shore leads started to freeze and “locked” the remnant
1GS ice sheet of the winter of 1981-1982 in the bay. New
ice also started to grow below the 1GS ice. Unlike the
previous growth season, due mainly to lack of travel
funds, no ice data was collected during the winter of
1982-83 until the early spring of 1983 when the AES/
NRC research team revisited the site long before the end
of the usual growth season. The third series of Mould
Bay experiments was conducted during the period 31
March to 10 May 1983.
The general view of the surface characteristics of the
ice cover on 31 March can be seen in the photograph
(Figure 5.16) taken from the top of Thunder Mountain.
This view clearly shows elongated hummocky surface
features very similar to the elongated snow hummocks
noticeable in Figure 5.12a and 5.15. Thus the surface
roughness of SY ice floes may be linked closely to the
surface features developed during the previous melting
season. The relief around the melt ponds and drainage
channels must, therefore, continue to influence subse-
quent ablation of ice at surface levels and later stimulate
the formation of snow drifts, wind‐driven compaction
of snow particles, and morphological changes in the
snow mass during the growth of the winter season of
1982-1983.
Ten equally spaced sampling stations were established
along the experimental line close to the path created by a
snow plough for ease of traveling with snowmobiles. The
snow depth varied between 0.1 and 0.6 m and, inciden-
tally, very similar to that observed in June 1982. The ice
thickness profiles across the bay along the experimental
line, shown in Figure 5.17, indicates that the old ice dur-
ing the past freezing season was located between stations
2 and 9 with a refrozen lead near station 7. This lead
undoubtedly was linked to the large crack mentioned
earlier. The thickness of the old, 2GS, ice that had gone
