PURPOSE OF RESEARCH
Ackley 1982, Mellor 1983) compared to spray-accreted
saline ice. Saline spray ice freezes rapidly compared to
Measurements were made aboard ship to character-
floating sea ice, forms on vertical surfaces in addition
ize superstructure spray and ice accretion. Weather, sea,
to horizontal surfaces, and is periodically flushed and
and ship operating conditions were measured by the
dried as more spray lofts over the bow and brine drains
ship's personnel, and sea water temperature and salin-
from ice at higher locations on the superstructure. This
ity were measured by the ship's crew and the CRREL
unique energy and mass environment for saline ice
research team (Ryerson and Longo 1992).
growth and evolution affects the mass of ice at various
Though the research cruise continued for about 40
locations on the ship, and its strength, physical, and
days, only a few days of spray and ice data were
crystalline properties.
recorded because of unsuitable weather and ship
operations. Seas were frequently calm, temperatures
METHODOLOGY
were typically higher than the freezing temperature of
sea water, and the ship was often stationary or moving
slowly and producing no spray because patrol duties
In two icing events aboard the cutter, 23 ice samples
required the launch and retrieval of small boats and a
were removed from decks, bulkheads, the gun mount,
helicopter. Nevertheless, sufficient data were collected
and lifelines (Ryerson and Longo 1992, Ryerson 1995).
to characterize spray and ice.
The first icing event occurred from 2225 February,
A previous report (Ryerson 1995) gives detailed
and the second from 1014 March. Ice samples were
information on bow spray duration, drop concentration,
removed from decks and bulkheads on 24 February and
drop size distribution and liquid water content, and the
12 and 13 March (three times on the latter date) as
general ice accretion and ablation conditions, as well
indicated in Figure 7. As shown in Figure 8, all samples
as thickness distribution. This report characterizes the
were taken on and around the forecastle because insuf-
physical structure and crystalline properties of ice
ficient ice accreted elsewhere.
sampled from the ship superstructure, and expands upon
Samples were removed, using a putty knife, in com-
observations made by us in an abbreviated paper
plete sections from decks, bulkheads, hatches, and
(Ryerson and Gow, in press).
cables of painted steel, painted aluminum, nonskid, or
polypropylene. They were immediately placed in clear
plastic freezer bags and sealed to prevent draining brine
ICE PHYSICAL AND CRYSTALLINE
from escaping. In addition, in-situ ice temperatures were
PROPERTIES
measured (Fig. 9). Though many samples appeared to
be nearly saturated on decks, no water freely ran from
In the 1960s, the Soviets measured the physical prop-
them as they were removed. Samples removed from
erties of spray-deposited ice on medium size fishing
bulkheads were always dry at the ice/substrate inter-
trawlers (Panov 1972, Golubev 1972, Smirnov 1972,
face.
Kultashev et al. 1972). Measurements were also made
Samples were kept on deck in freezer bags during
by Japanese researchers on ships ranging in size from
the duration of each 30- to 60-minute sampling excur-
trawlers to patrol boats (Ono 1968, Tabata et al. 1963,
sion. They were then moved in an insulated container
Iwata 1975). Supplementary work has also been done
to the officer's galley refrigerator freezer compartment,
in saline wind tunnels, especially to measure salinity,
approximately amidships. The temperature of the
freezer compartment was approximately 18C. Within
brine volume, and porosity (Makkonen 1987, Gates et
al. 1986), and with models to simulate ice accretion
minutes to a few hours, samples were moved again in
amount with location on the superstructure, and icicles
an insulated container to the ship's main food locker,
also at 18C (Ryerson and Longo 1992). The samples
(Lozowski and Szilder, in press). Measurements have
not been made on ships in the Western Hemisphere,
remained in the food locker within picnic coolers until
and none have been made on large ships except by
May 1990.
CRREL (Ryerson 1995). Ice properties such as thick-
Immediately upon the ship's return to Alameda, Cali-
ness and density affect the mass of ice accreted on decks
fornia, at the end of the cruise, the coolers of bagged
and bulkheads. In addition, crystal structure, as well as
ice were packed with dry ice. The still-bagged ice
physical properties, provides information about the his-
samples were kept sealed and separated from the dry
tory of the ice and its depositional environment.
ice by layers of cardboard. The coolers were then air-
The properties of saline ice formed by direct freez-
shipped to CRREL within 24-hours and placed in cold
ing of ocean water, and its evolution with time and
storage. The ice was stored in coldrooms at tempera-
tures of 12 to 30C for 6 to 7 months before we made
location, are reasonably well understood (Weeks and
5
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