Table III. Snow depth on the ground (cm). 



(ESSA climatological data.) 



1961/62 62/63 63/6* 6<^/65 65/66 66/67 67/68 68/69 69/70 MEAN 



upper layer to softer snow below; but the contact between these harder layers and the depth hoar 

 crystals of the lower layer is always sharp, with an abrupt and easily measured difference in snow 

 density. 



Ordinarily the snowpack on the tundra is about 40 cm thick between raicrorelief such as hum- 

 mocks and tussocks and 20 cm thick or less over their tops. A 40-cm snowpack typically has hard 

 wind slab for the top 20 cm, moderately hard snow for the next 10 cm, and depth hoar with negligible 

 hardness for the bottom 10 cm. 



During the 1970-71 winter, detailed investigations of the snowpack formation and metamorphism 

 are planned. These began as the fall snow cover accumulated. Temperature measurements within 

 the snow cover and in the plant canopy are being made in typical lemming habitats. 



The 1970 Barrow summer climate was cooler and drier than usual. The average monthly air 

 temperatures were below normal for aU three months. The summer was extremely dry with only one 

 storm exceeding 2.5 mm of precipitation in a 24-hour period. The monthly averages, totals and de- 

 partures from the normal are as follows: 



Although air temperatures rose above freezing during the last week in May, daily average 

 temperatures did not remain above freezing until 15 June. The daily mean, maximum and minimum 

 air temperatures are shown in Figure 8. Spring runoff began through Footprint Creek on 14 June, 

 although many snow-free tundra areas were in evidence by that date. Due to the light snow cover 

 and the lack of June or early July precipitation, sustained runoff ceased during the first days in 



16 



