Geology Reference
In-Depth Information
(Figure 5.33a) except for the top 0.1 m of granular ice with
a mixture of snow and frazil crystals. This FY ice was,
therefore, very similar to the ice found in Mould Bay for the
1981-1982 growth season, presented earlier. The 5.1 m long
core taken from a relatively flat area of MY floe (marked in
Figure  5.32) showed columnar‐grained, S3 type of ice
from the top to the bottom, as illustrated in Figure 5.33b.
There were, however, five zones of ice separated by four
distinct “interfaces” in this ice core as demonstrated in
Figure 5.33c. The continuity of columnar‐grained crystals
across the interface, at a depth of 3.83 m, between the old
ice that moved inside the bay and the new ice grown during
the 1983-1984 is shown in Figure 5.34.
Since the top layer of the MY floe ice core had S3 type
of structure, it ruled out the possibility of the site's ori-
gin in a melt pond in which the tidal water current could
certainly not exist. The habit of the grain structure in
this core, although columnar, showed some angular
characteristics at various depths. Moreover, air bubbles
were concentrated along all the interfaces. The inter-
faces at 0.35 and 1.52 m exhibited marked differences in
the vertical salinity profile, but the interfaces at 2.28 and
3.83 m did not show any noticeable differences.
Consequently, it is highly possible that the MY floe was
a 5 year old floe.
Since the MY floe along with all the old ice moved
inside the Mould Bay before the start of freezing in
September, 1983, the bottom layers in all the old floes
grew during the winter of 1983-1984. Consequently, the
ice below the interface at 3.83 was S3 type (Figure 5.34)
with c axis of the grains and subgrains in the horizontal
plane, preferably oriented parallel to the longitudinal axis
of the bay, was similar to the S3 ice at station 9 shown
Mould
Bay
MY-R
MY
Figure 5.32 AES‐Star‐1 airborne X‐band (HH polarization)
SAR image of the Mould Bay ice cover on 10 March 1984,
showing many old floes frozen into the matrix of the FY ice of
1983-1984 winter.
(a)
(b)
(c)
0.0
0.0
0.00
Borehole
jack test
depth, -20°c
Borehole
jack test
depth, -20°C
0.35
0.5
0.5
0.25
1. 0
1. 0
0.50
Borehole
jack test
depth, -10°c
1. 5
1. 5
1. 25
0.75
2.0
2.0
1. 00
2.28
Mould Bay
4-peg floe
9 April 1984
Mould Bay
norland floe
(site 3)
29 March 1984
2.5
2.5
1. 25
3.0
3.0
Colimnar
Interface
1. 50
3.5
3.5
Snow ice
Snow ice
Frazil
3.83
1. 75
4.0
4.0
Station 9. Mould Bay, 22 March 1984
Snow ice
2.00
4.5
4.5
Columnar-grained ice
5.0
5.0
2.25 01234
Salinity. ‰
01 23
01 23
45
5
67
Salinity. ‰
Salinity. ‰
Figure 5.33 Vertical salinity and grain structure of three different types of ice at Mould Bay in March 1984: (a)
columnar‐grained S3‐type annual FY ice at station 9 along the experimental line, (b) columnar‐grained S3‐type
ice in MY floe with four distinct interfaces, and (c) rubble‐field ridged ice in MY‐R floe (named as 4-peg for
identifying during field work) with new S3 ice growth near the bottom [ Sinha , 1987a].
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