22 
Fig. 8. Ajr temperature plot for May 1972. 
Temp, °c Density, g cm®> 
elie) SIoy Sh} io) 010 0.20 0.30 040 0.50 
120 T Teal ae T i r a =]; 
arene: 
100 leseecae| 
— 80 EES — 
£ 60 felts 
40 | al 
20 ip 
4$ 
. 
. 
° eal: 
AAA 
A A 
0 x 
a. 28 meters east of P2 
(8 meters east of road) 
Temp, °C Density, g cm? 
15 -10 5 0.20 0.30 0.40 050 
=: T T us i = 
We ate 
PROEAR LA jaey 
b. 40 meters east of P2 
Density, g cm”® 
0.20 fe) po 040 0.50 
: = fou __0: 
ili 
c. 90 meters east of P2 
Temp, °C Density, g cm> 
= Sie Olas. fo) 0.10 0.20 0.30 040 0.50 
7 aa a= cscleel 
E40 T T + + | 
o “. -+ , 
© 
a 20 fn 
os . A A A 
d. 200 meters east of P2 
Density, g cm™> 
0.20 0.30 040 0.50 
T 
SS pat = 
j 
e. 300 meters east of P2 
Fig.9. Pit data from Prudhoe Bay. 
Based on the data from mid-May (Table 1 
and Fig. 8), when daily range of air temperature 
was 10 to 20°C, let us consider a daily tempera- 
ture variation of 12°C (from -1°C to -13°C) 
and calculate the range of temperatures at 10 cm 
depth intervals in a snowpack 40 cm thick. The 
range at a selected depth Z is given by 
-Z y IT 
aP 
where T., is the temperature amplitude 
TR = 2T,e 
at the surface 
Z is depth below snow surface (cm) 
a is thermal diffusivity (cm? sec’') 
and P is the period, i.e., 1 day (86,400 sec) 
The calculated results are summarized in Table 
3 and Fig. 11. These values are consistent with 
the magnitudes of temperature change observed 
in the snowpack during the cooling trend be- 
tween 14-16 May (Fig. 10). We can now estimate 
the daily heat exchange in the snowpack during 
May by asimple calculation. To do this, we shall 
use the bottom 40 cm of density data from Fig. 
Qe (i.e., neglect the top 6cm of fresh snow) 
together with the temperature ranges obtained 
in Table 3 with diffusivity = 0.0050 cm? sec’'. 
The calculations are summarized in Table 4. 
In mid-April 1972 the cold content of the 
snow cover at Prudhoe Bay was about 100 cal 
cm?, and the daily heat exchange in the snow 
was about one-quarter of this. When melting 
occurs at the snow surface, it is accompanied by 
localized percolation of meltwater which re- 
freezes to form a complex net of ice glands, 
lenses, and layers within the snow. The amount 
of heat transported downward into the snow by 
the percolation process is about 45 cal cm? for 
each cm of ice thickness formed. Some of this 
heat is lost in the daily cooling cycle, but a 
significant amount goes into warming the lower 
parts of the snowpack. When melting begins to 
wet a thick part of the snowpack, the tempera- 
ture profiles take the shape of the dashed line in 
Fig. 10. A gradient exists in the lower part, but 
it varies laterally in the snow because of the 
