tal size measurements of 19 of the 23 samples collected
inclusions were frequently observed within crystals.
during the cruise are presented in Table 3; also, bubble
This might be interpreted as evidence of incidental grain
sizes were obtained for 16 of the 19 samples sectioned
growth (recrystallization) that most likely occurred in
for microstructural analysis.
the accreted ice some time after its formation but prior
Descriptions of the microstructural characteristics
to sampling or sectioning.
of a selection of samples of accreted ice follow.
Crystal orientation observations
We made no attempt to determine preferred crystal
RESULTS AND DISCUSSION
orientation using universal stage techniques. However,
after examining the general nature of interference color
February icing event
changes in the crystal aggregates when a section was
Vertical surfaces
rotated between crossed polarizers, it appeared to us
Sample F3. This is a bulkhead sample collected
that c-axis orientations were substantially random.
Dimensional orientation of crystals was, however,
0.5 m above the deck and from the same general
observed in sections cut from icicles. The results of crys-
location as samples F4 and F5. Sample F3 (Fig. 11)
Figure 11. Sample F3,
taken from the face
of the forward bulk-
head and about 0.5 m
above the deck sur-
face (scales in milli-
meters).
a. Sample location.
b. Thick sections photographed in
natural light.
c. Thin sections photographed in natural light (right) and between crossed
polarizers (left).
15
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