importance of initial ice thickness and snow cover thickness is clearly 

 shown in Figure ?, where curve 1 indicates the variation in time to 

 freeze 5 cm. of ice for different initial ice thicknesses and curve 2, 

 the time required to freeze the same amount of ice with varying snow 

 thicknesses. 



5. Wind 



Figure 8 shows the effect of wind velocities of 20, 30, and 40 

 miles per hour on rate of ice growth for A^ - 1 cm, <^~t » 53 cm. and 

 § = 10 cm. Under these conditions a change of 10 miles per hour in 

 wind velocity has very little effect on ice growth. However 9 for lower 

 values of wind velocity the effect is marked 



6. Salinity 



The effect of sea water salinity is indicated in Figure 9 Under 

 the conditions indicated on the figure a slightly greater ice thickness 

 accumulates for the length of time in fresh water than accumulates in 

 salt water. However, the two curves do not show much difference in 

 growth rate of ice due to the salinity. 



7. Effect of the Heat of the Water Mass 



None of the formulas so far considered has attempted to evaluate the 

 effect of the heat of the water mass itself on the growth of the ice 

 sheet. In the presence of warm currents or where the thickness of the 

 layer subject to convectional cooling is great, the effect of the heat 

 of the water mass is appreciable. By taking the heat of the water mass 

 into consideration, a formula can be developed which is identical with 

 Equation 22 with the exception of an additional term which represents 

 the heat of the water mass. 



The form of this additional term is as follows $ 



— r ir »-2n-! 2 ] f tr v 2n-l ? 1 



S 62 C 2P 2(VT X )H m 00 expU 2 (2 X -H-) f ( J-expU 2 (Y x Tn ij 



k'fl[«+fl!r(Tx-0>] n=1 ^-\f {2k) 



where: C 2 - specific heat of sea water, 

 P~ m density of sea water, 

 T2 a average temperature of the layer in °C, 

 Tx= freezing point of sea water in °C, 

 H m ** thickness of layer expressed in meters, 

 /> a =. density of ice, 

 C-jl - specific heat of ice, 

 © = equivalent temperature in "C^ 

 A 2 - turbulent heat conductivity of sea water, 



18 



