a. Sample location.
b. Thick sections photographed in
natural light.
c. Thin sections photographed in natural light (right) and between crossed
polarizers (left).
Figure 24. Sample M10, taken from the port bulkhead of the 5-in. gun hous-
ing, approximately 1 m above the deck (scales in millimeters). Thick sec-
tions suggest layering, and thin sections show a mixture of rounded and
recrystallized ice grains. The dark structure in the upper right corner of the
section is attributable to the coalescing of several brine pockets.
and about 0.5 m port of the windlass. Microstructurally,
in. gun base (Fig. 26). The bulk salinity of this sample
it consists of an intermixture of large, somewhat shape-
measured 16.2‰, which, together with the density of
0.868 Mg m3, yielded entrapped air and brine volumes
less crystals with much smaller subrounded grains. The
coarser crystals were among the largest measured in
of 9.3 and 30.8% at a measured in-situ temperature of
2.4C. The crystalline texture of this sample is char-
any sample collected on the cruise. They were certainly
the largest observed in deck-accreted ice (Table 3). In
acterized by rounded, somewhat elongated grains
coarsely crystalline deck samples, such as illustrated
immersed in brine. Among deck samples, this particu-
by this sample, layering is present but sometimes lacks
lar sample exhibited the second largest mean crystal
cross section (1.33 mm2) and the largest mean bubble
continuity. A bulk salinity of 13.7‰ was measured,
which, when used in conjunction with a density of 0.865
diameter (0.29 mm).
Mg m3 and an in-situ temperature of 1.6C, gives
values of 40.1 and 10.3% for the volumes of brine and
Sample M13. This sample of deck icing (Fig. 27)
air incorporated into the ice. A mean gas bubble diam-
was obtained from ice that had accreted to a thickness
eter of 0.25 mm was also measured.
of 2.4 cm, approximately 2 m in front of the 5-in. gun
27
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