Introduction and Site Description 35 



ice melt in large lakes, such as ice albedo, crystal orientation, moat 

 formation, and wind action, have been reviewed by Hobbie(1973). 



Runoff begins on the day the snowpack becomes completely 

 saturated with water and the maximum discharge occurs within 24 hours. 

 In the next 4 days, 40 to 60% of the total spring runoff takes place— this is 

 still before there is any thawing of the frozen ground. Around Barrow, the 

 runoff from polygonal ground begins in the first half of June (it was 9-1 1 

 June from 1970 to 1973) and lasts until the first week in July. Runoff in the 

 sloughs and larger creeks is delayed and prolonged. In the Colville River, 

 for example, the maximum runoff does not occur until three weeks after 



Radiation 

 Balance 



37 



1 



Heating 

 Soil Snow 



Heating 

 Air 



cal cm day" 



23 



Melting/ 

 Evaporation 



i 



a. Pre-Melting 

 29May to3Jun 



139 



n 



I 



30 



^ 



33 



i H 



b. Snow Melting 

 4 to 13 Jun 



380 



c. Post- Melting 

 14 to 17 Jun 



238 



I 



26 



H 



70 



H 



83 



277 



d. Mid-Summer 

 15 to 28 Jul 



97 



H 



T 



77 



157 



22 75 



e. Freeze -Up 

 25 Aug to I Sep 



1 



28 3 



i I 



36 



f. Mid-Winter 

 5 to 10 Feb 



T 



FIGURE 2-5. Heat balance for Barrow tundra for six 

 characteristic periods. The width and direction of the 

 arrows and the numbers at the base of each arrow in- 

 dicate energy flux directions and rates. (After Weller 

 and Holmgren 1974). 



