Climate, Snow Cover, Microclimate, and Hydrology 43 



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-45 



-40 



-35 



-30 



-25 



-20 



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March 1971 



FIGURE 2-7. Temperatures in the snow during 1-6 March, the coldest 

 period in 1971. The numbers on the graphs give the distance above the 

 ground surface at which snow temperatures were measured. 



warmer conditions at the snow/ground interface (Figure 2-7). Although 

 the temperature at the air/snow interface during the 6 days shown in Fig- 

 ure 2-7 ranged between -47 °C and -35 °C, the temperature at the 

 snow/soil interface stayed within a degree or two of -26 °C. The snow 

 temperature phase lag and amplitude attenuation indicate that the effec- 

 tive thermal diffusivity of the snow is larger by a factor of 3 to 4 than 

 that of the organic materials just below the snow/soil interface. Thus, 

 the rather stable and relatively warm thermal environment at the snow/ 

 soil interface is produced by the mass of snow overlying the interface and 

 not by the thermal properties of the snow cover per se. Increasing depths 

 of snow favor a more moderate snow/soil interface environment, with 

 reduced temperature extremes and a higher mean temperature. 



The typical two-layer snow structure is the most favorable environ- 

 ment for small mammals like lemmings. The loose depth-hoar layer gives 

 little resistance to burrowing, and the hard wind slab provides protection 

 from wind and from predators. At a snow fence site (Slaughter et al. 

 1975, Outcalt et al. 1975), where the maximum snow depth was increased 

 to nearly 2 m by drifting, there was evidence of much more intense lem- 

 ming activity and nesting than on the surrounding tundra, where the 

 natural snow depth was less than 0.5 m. Other mobile organisms also 



