38 



S. L. Dingman et al. 



FIGURE 2-4. Development of the 1970-71 snow cover on the Biome re- 

 search area. Each point represents the average of 15 measurements. 

 (Weller and Benson, unpubl.) 



directly or indirectly, on food-chain members harbored within the snow 

 cover. Thus a knowledge of snow distribution and structure is an essen- 

 tial part of the understanding of tundra ecology (Pruitt 1960, Formozov 

 1961). The most detailed work on the nature of the snowpack on the 

 Alaskan Arctic Slope is reported in Benson (1969) and Benson et al. 

 (1975). 



The major surface processes during the winter are the accumulation 

 of snow, its redistribution by wind, and the transfer of mass and energy 

 within the snowpack. Over most of the tundra at Barrow, the snow 

 builds to a thickness of about 20 cm within 10 to 20 days after freeze-up, 

 following which it continues to increase very slowly in thickness (Figure 

 2-4). The initial snow cover markedly reduces surface roughness and per- 

 mits more effective snow drifting. Snow is deposited in drift traps and, as 

 the winter progresses, the surface relief becomes more and more sub- 

 dued. 



With the establishment of the snow cover and the virtual disappear- 

 ance of solar energy input at the surface the net radiation becomes nega- 

 tive. The radiational cooling at the surface sets up fairly steep tempera- 

 ture inversions above the ground, so that both atmosphere and ground 

 supply heat to the surface, one by eddy diffusion, the other by conduc- 

 tion. These conditions induce a flow of heat and moisture from the soil 

 surface upward through the snowpack, driven in part by wind and baro- 

 metric fluctuations (Benson 1969). There is a consequent general drying 

 of the upper soil layers and formation of depth hoar in the snowpack. 

 This results in a net gain of moisture in the snow because of the upward 

 transport of water. Some condensation at the snow surface also adds to 

 the mass of the snow (Weller and Holmgren 1974a). 



Although fresh snow continues to accumulate throughout the win- 

 ter, the steady winds constantly reshape the pattern of the snow cover. 

 Across the smoothed surface, barchan-type dunes form and move during 

 storm periods. During less windy periods, these dunes stabilize and 

 become drift traps for future storms. Exceptionally high winds may 



