&W - vapor pressure of the water in inches Hg 0i , 



e a - vapor pressure of the air in inches Hg,, 



T w = temperature of the water in degrees F», 



T a <s temperature of the air in degrees F. 



eff. Qb (effective back radiation) « difference between 

 temperature radiation of the sea surface and long-wave radiation from the 

 atmosphere, 



t » time in units designated above,, and 



r ~ fractional part of the incoming radiation reflected from 

 the sea surface. 



The ice potential computations determine the amount of sensible heat 

 which must be removed from the water column prior to the initial formation 

 of ice. For example, let this value be Q„. Then setting Q p « Qfc ~ Q Q - Q a t, 

 and solving for t gives the number of days between the time that the ocean- 

 ographic measurements were made and the time ice will form. 



D. METHOD OF COMPUTING ICE GROWTH 



From the time oceanographic observations are made until the time ice 

 forms, it is assumed that the heat exchange results from incoming radiation, 

 back radiation, and evaporation. After ice forms, the processes by which 

 heat is removed from the water column are altered considerably. Any heat 

 that is then removed from the water must be conducted through the solid 

 layer of ice above it. Thus, the rate of further heat loss is determined 

 by the temperature gradient through ice and snow. Hence, assuming steady- 

 state conditions for finite increments of time, 



cKQt+QJ AT, AT (^ 



dt K i \ " k s \ 



where, Qp is the amount of sensible heat loss (in kg, cal.), 

 Ql is the amount of latent heat loss (in kgo cal,), 

 k l is the heat conductivity coefficient of sea ice, 

 k s is the heat conductivity coefficient of snow, 

 A Tjl i s the temperature difference between the upper surface of 



the ice and freezing point of sea water (in °C), 



A T s is the temperature difference between the surface of the snow 



and the surface of the ice (in °C), 



ll is the thicknesr of the ice in om s 



l s is the thickness of the snow in cm, and 



l s is the mean snow cover over a finite period of time*, 



Since AT =aTj +AT 3 , where A T is the temperature difference between the 

 freezing point of sea water (taken at -1«>8 C.) and the snow surface tem- 

 perature, and from (7) 



AT.V1. «0 



