Table 3. Dates of first significant ice and ice-out for northern Cook Inlet (defined as 10% ice concentration at the Phillips Platform)

Figure 10. Dates of significant ice formation at the Phillips Platform with respect to freezing degree-days (assuming a base temperature of 3.9C).

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Table 3. Dates of first significant ice and ice-out for north-

ern Cook Inlet (defined as 10% ice concentration at the

Phillips Platform). Extreme minimum and maximum dates

are in bold. The 1984-85 season experienced an initial

ice-out and refreeze on Feb. 13th. (After Brower et al.

1988.)

Ice-Out

Oct 17

May 15

Mar 10

Dec 17

*Assumes only the first "First Ice" period and last "Ice-Out" period for

the 1984-85 season.

the atmosphere. While the latter three factors remain

Although the number of years studied was small

nearly constant from year to year, the fact that ice con-

(11 winters) and the scatter large, one relation-

ditions are highly variable from season to season in-

ship was found to be significant. Ice formation in the

dicates that other factors are involved. The ice condi-

Upper Inlet correlated reasonably well with Anchor-

age FDDs, using a base of 3.9C. Their analysis

tions are also related to topographic, meteorological,

oceanographic, and sometimes even geological phe-

showed the Lower Inlet to be much less well corre-

nomena. The factors that can vary greatly and typi-

lated. These data are shown in Table 4 and plotted in

cally favor ice growth (Brower et al. 1988) include

Figure 10.

The hydrodynamic and meteorological environ-

Radiational cooling,

ments are responsible for the large quantity of ice that

Cold, freshwater influx from stream flow discharge,

is produced annually in Cook Inlet. The long season

Snow falling on the sea surface and melting, and

of freezing temperatures, the large tidal range, the high

Cold air mass advection.

current velocity, and the shallow bottom depths all

favor ice production. The latter three make for a tur-

On the other hand, many factors discourage ice

bulent water column and continuous surface flux that

growth in Cook Inlet. Examples of the more predict-

inhibits the growth of a stable ice cover, which can act

able are

as an insulating blanket and prevent heat exchange to

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