Climate, Snow Cover, Microclimate, and Hydrology 39 



TABLE 2-2 Types of Snow Found on the 



Windblown Arctic Coastal Plain 



*The density ranges are approximate, but they indicate the 

 differences one may expect between the various layers. 



remove or reshape the old dunes and even reexpose some of the vegeta- 

 tion. The interaction of wind effects and transfer processes within the 

 snowpack produces four snow types (Table 2-2) and four typical snow 

 structures: 



1. A hard, fine-grained, high density, windpacked layer overlying a 

 soft, coarse-grained, low density layer. The upper layer is fre- 

 quently a wind slab; the lower is almost entirely depth hoar. This 

 two-layer structure is the most common, being present over about 

 80% of the open tundra. 



2. The hard wind slab layer alone, found over about 15% of the 

 open tundra. 



3. The soft depth hoar alone, covering about 5% of the open tun- 

 dra. 



4. A complex, deep snowpack, largely wind slab and medium- 

 grained snow, in natural drift traps such as creek bottoms. 



The development of the two-layer structural type as seen in Figure 

 2-5 is a direct consequence of the depositional history of the snow. The 

 rapidly deposited snow layers of September contain few significant wind 

 slabs and are the primary units in which depth hoar develops. As the 

 season progresses, the wind causes very hard snow layers to form as 

 small increments of new snow are added. Admixtures of silt or fine sand 

 from exposed roads or dunes, or of particles of vegetation, strengthen 

 wind slabs. 



The continual heat flux from the soil below the snow keeps the soil/ 

 snow interface temperature above that of the upper snow surface. This 



