It should be noted that the absolute extremes of cold are expe- 

 rienced in the Subarctic rather than the Arctic. There is no 

 nearby ocean area to help modify the climate. The Alaskan 

 ranges cut the Yukon and Mackenzie valleys off from the maritime 

 western winds. The active layer of the permafrost quickly freezes 

 during the long nights of semi-darkness of winter, and the rivers 

 and lakes become frozen and snow-covered. In the winter, cold 

 air from northern Greenland and the Arctic Sea sweeps across the 

 prairie in the Baker Lake area and, under anticyclonic control, 

 flows into the Yukon where the clear skies and stagnant air con- 

 ditions promote tremendous refrigeration. Temperatures have 

 been recorded as low as minus 76° F. at Tanana, minus 69° F. 

 at Whitehorse, minus 74° F. at Fort Snag, and minus 78.5° F. at 

 Good Hope. This same area experiences high summer tempera- 

 tures. The range of the temperatures is extreme, with average 

 annual ranges about 134° F. 



With all this extreme low temperature, there is relatively little 

 snowfall. Three to ten inches a month is the general average. 

 Over much of the area the wind keeps the snow moving about, 

 although the forests act to break the force of the wind. The 

 heaviest drifts of snow are just south of the treeline where snow 

 from the open tundra accumulates. The wind which carries the 

 snow across the open areas is slowed in velocity as it strikes the 

 forests. With less velocity its carrying power is reduced, and 

 snow is deposited in high drifts just inside the forest area. 



VEGETATION AND ANIMAL LIFE 



Over most of this region there is a heavy growth of coniferous 

 forests. These dense forests are interspersed with peat bogs and 

 muskegs. Like the extensive taiga of the Soviet Union, these for- 

 ests have been ravaged by fires and exploited by lumbermen. In 

 the more exposed areas and in the northern fringes of the forest, 

 the trees are smaller and more bushy. In contrast to these forested 

 areas, the Aleutian Islands are essentially treeless. Grass, shrubs 

 and tundra vegetation cover most of the islands, although many 

 barren rocky areas exist without noticeable plant life. 



The largest animal in the North American Subarctic is the 

 Kodiak bear weighing from 1,200 to 1,500 pounds. However, his 

 habitat is essentially restricted to the one island, and elsewhere 

 the brown bear, wolves, foxes, mink, marten, beaver, and otter 

 are common. The deer, moose, and caribou are also found in the 

 forests. 



56 



