38 
to the Bechtel Garage in 1973. The albedo data 
at Prudhoe Bay do not represent the undisturb- 
ed tundra since the snow in that area is generally 
contaminated by dust from industrial activities, 
mainly road dust, and by natural dust from sand 
dunes in the Sagavanirktok River delta area. 
The actual measuring locations were selected 
to represent approximately average snow condi- 
tions. Albedo measurements over a_ shallow 
snowpack in situations with high incoming solar 
radiation are extremely sensitive to any man- 
made or natural disturbances. Although care was 
taken to disturb the snowpack as little as possi- 
ble in connection with installation of the equip- 
ment and daily maintenance and inspection, 
some disturbances of the snowpack could not be 
avoided. These disturbances had a noticeable 
effect on the breakup patterns around the radio- 
meter stands. 
The variations of the incoming short-wave 
radiation and the albedo at Prudhoe Bay for the 
summers of 1972 and 1973 are given in Fig. 22. 
The general features of the radiation regime for 
coastal tundra are well-known since the radia- 
tion climate at Barrow has been investigated for 
many years (Ray 1885; Thornthwaite and 
Mather 1956, 1958: Kelley et al. 1964, 1969; 
Lieske and Stroschein 1968; Lieske and Bailey 
1969; Weaver 1969, 1970; Weller et al. 1972, 
1974; Maykut and Church 1973). During break- 
up, there is generally a sharp drop of the albedo 
from values above 80% to values of about 
15-20%. The lowest values are obtained when 
the tundra is wet (Weller et al. 1972). At 
Prudhoe Bay the albedo generally varied be- 
tween 10 and 15% after breakup in 1973. 
One of the most striking features in Fig. 22 
is the high variability of the incoming radiation. 
The cloud conditions along the coastal zone of 
the Arctic Ocean are similar throughout the 
summer with persistent decks of low stratus. On 
the average the National Weather Service sta- 
tions at Barrow and Barter Island have cloudi- 
ness at or above 8 tenths from May to October 
with a main maximum in August-September and 
a secondary maximum in May. The decrease in 
cloudiness in the middle of the summer has been 
ascribed by Sverdrup (1933) to a weaker inver- 
sion during that period. 
The transmissivity of the stratus for solar 
radiation is highly variable. Although the stratus 
a. 24 May 1972 (NE view). 
Le 
b. 5 June 1972 (S view). 
Fig. 18. Sequential photographs (above and op- 
posite page) of BP Gathering Center No. 7 dur- 
ing breakup 1972. (Arrow located on east side 
of GC- No. 1 and pointing due west). 
