Geology Reference
In-Depth Information
History on sea ice observations was actually made in
Mould Bay during the winter of 1981-1982. Never before
were hourly weather data (air temperature, snowfall
activities, wind and sky conditions, etc.) collected at a
ground‐based location adjacent to sea ice covers sub-
jected to long-term multidisciplinary observations. In
addition to the data collected on microstructure and tex-
ture of young (up to 300 mm in thickness) sea ice during
the first field trip to Mould Bay in September-October
1981 (described in detail in section 4.4.1), the growth of
ice and snow cover at various stations across the 7.2 km
wide Mould Bay was monitored every week during the
major growth period for FY sea ice including the most
difficult periods of the polar nights, from 31 October
1981 to 13 June 1982. The staff of the weather station
shared their efforts and volunteered to collect the data
through the extremely cold and dark polar nights.
Traveling on the ice in the dark was by no means pleasur-
able. They actually risked their lives on several occasions.
By carrying out more than their routine observations at
the weather station, members of the station filled the gap
in the intervening periods between field trips conducted
by members of the research teams. Normally, these types
of details on human aspects of science and engineering
are not covered in technical topics. Since snow, ice, and
water play the most important roles in shaping our life
and the environment we live in, scientific aspects of these
materials cannot be discussed without referring to the
human and environmental aspects.
The staff of Environment Canada's Mould Bay weather
station voluntarily recorded every possible environmental
data they could collect. Often they noted down their
observations on the sea state on an hourly basis. Their
observations helped us to analyze the prevailing growth
conditions for sea ice from the very beginning. According
to their observations, the freeze‐up in the water of Mould
Bay started on 24 September 1981 near the eastern shore
close to the weather stations. The shoreline area was full
with slush (thick grease ice) that was produced during a
storm that occurred a few days earlier, coming from the
Arctic Ocean with predominant wind direction from the
west. Following the storm, the wind died down and
remained so for more than a week. It was not only very
calm for almost 10 days but there was no snowfall except
for traces. During this calm period the slush around the
eastern shore started to solidify first. Thereafter, the
freezing front started to move very quickly toward the
west, away from the eastern shoreline. By 26 September,
the entire bay from shore‐to‐shore was covered with a
thin layer of dark gray ice. The first 10 days after the
beginning of freezing were almost ideal conditions for ice
growth. The entire bay, with the proximity to the weather
station, became a giant mesoscale laboratory. For a sea
ice researcher, like the second author (N. K. Sinha), it was
0
140
Mean
temperature
Snow
depth
-5
Maximum
120
-10
100
-15
80
-20
60
Minimum
-25
40
September
-30
20
October, 1981
-35
0
0
10
20
30
40
Freezing days
Figure 5.6
Variation of daily maximum, minimum, and mean
air temperatures, and snowfall, recorded at the AES High Arctic
Weather Station of Mould Bay, after the first freezing day of 24
September, 1981 (N. K. Sinha, unpublished).
like a dream come true. Never again after this experience
and experiences in the next few years at Mould Bay, did
he use his meticulously designed (and much loved) 2 m
deep‐sea salt‐ice tank at NRC laboratory in Ottawa for
simulating unidirectional heat flow and growing direc-
tionally solidified (DS) saline ice. Sea ice studies can and
should be performed only on natural sea ice and as much
as possible under field conditions and in the field.
During the crucial initial periods of growth under
calm conditions, the mean air temperature was below
-8°C and reached as low as -19°C as can be seen in
Figure 5.6. Daily temperature and snowfall amount for
the period when young ice existed and developed into
FY ice is shown in Figure 5.6. On‐shore observations
indicated that the young ice cover was fairly homogenous
and essentially free from any snow cover. However, it was
thought to be too risky to operate on the ice sheet until
after one week of freezing. From years of field experience
in Eclipse Sound [
Sinha and Nakawo
, 1981;
Nakawo and
Sinha
, 1981] and simulated laboratory experiments in
Ottawa, the new snow‐free ice cover in Mould Bay was
expected to grow at a rate of about 30 mm/day. In 7 days,
the ice sheet should be around 0.21 m. This thickness was
calculated to be safe for slowly driving a snowmobile on
the cold sea ice cover, provided the rider wears heavily
insulated floater suits as precautions.
On 2 October when the air was still very calm and
the temperature was -12°C, but decreasing with time
(Figure 5.6), the first series of 100 mm diameter ice cores
and large full‐depth blocks of ice (for strength tests) were
sampled. They were recovered from areas about 2 km
(marked as station 3 in Figure 5.4) from the shoreline to
avoid the previously covered zone of slush. The surface
was found to be essentially free from snow and the new
ice was extremely uniform in thickness. The thickness did
