Table 2. Ice sample properties.

Table 2. Ice sample properties.

Bulk

Air

volumed

Samplea

surface

(cm)

(‰)

(%)

and salinity measured at CRREL.

cTemperature of ice measured in situ during sampling on USCGC Midgett. See Figure 7 for air temperatures during

sampling. Density measured at CRREL.

dComputed volume of entrapped air and brine, and total porosity at shipboard ice temperature (after Cox and Weeks 1983).

eSample temperatures were estimated from the mean of other ice temperatures in same sample period.

fExperimental ice removal panels installed by the U.S. Navy David Taylor Model Basin atop main hatch cover and on portion

of starboard forward bulkhead.

gTemperature not known with sufficient accuracy for computations.

caused by changes in air temperature and seawater ther-

sanding to a thickness of 1.2 to 3.2 cm, finished samples

containing about 50 to 340 cm3 of ice. Each sample

mal flux, suggest that superstructure icing is not a simple

was measured with digital calipers to 0.02-mm accu-

accretion process, but a series of accretionablation

racy at three locations in each dimension, and its vol-

episodes related to the thermally limited, mass limited,

ume was computed from the mean of each dimension.

and maximum accretion zones discussed earlier in this

Ice mass was measured to the nearest 0.01 g, and den-

report and by Ackley (1985). These accretionablation

sity was computed on the basis of the measured masses

sub-events are likely to influence ice physical proper-

and volumes of the samples. It is estimated that densi-

ties and crystallography.

ties are correct within 1% of their true values at the

measurement temperature.

ICE PHYSICAL PROPERTIES

Ice density, coupled with thickness, determines the

mass of ice at various locations on the ship, and has a

Density

large effect upon the ultimate strength of the ice and

how well it adheres to the substrate (Smirnov 1972).

Ice used for measuring density and salinity was sec-

tioned from the larger samples removed from the ship.

Ice densities measured during the February and March

icing events ranged from 0.69 to 0.92 Mg m3 (Table

A bandsaw was used to cut the samples into rectangu-

lar slabs with sufficient width and length to yield, after

2). Ice densities on horizontal surfaces were 1.2 times

11

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