I. INTOODUCTION 



This report presents available frost degree day data and sea ice 

 information for selected arctic harbors. Emphasis is placed on three 

 general categories of data: (1) cumulative frost degree days, (2) ice 

 growth and disintegration, and (3) harbor breakup and freezeup dates. 



II. METHOD OF COMPILATION 



A. Frost Degree Days 



Frost degree day curves were drawn for the 5^ arctic and subarctic 

 stations identified in figure 1 and listed in table 1. A frost degree day 

 is defined as a daily mean temperature 1°F below an arbitrary base of 32°F. 

 The frost degree day curves were based on mean monthly, mean daily maximum, 

 and mean daily minimum temperatures. These three parameters were used to 

 construct corresponding frost degree day curves, which give a normal frost 

 degree day accumulation, and an envelope showing maximum and rainimun) frost 

 degree day values for each station. These curves, together with a mean 

 temperature curve, are shown in figures 3A through 60A. 



b. Ice Growth 



Associated with the frost degree day curves are corresponding ice 

 growth and disintegration curves (figures 3B through 60B) . Two types of ice 

 growth curves are depicted in this report: (1) a theoretical curve based on 

 ciomulative frost degree days, and (2) an empirical curve based on observed 

 ice thickness data. At the stations where ice thickness data were available 

 for at least 3 years, empirical curves were constructed for normal ice growth, 

 as well as for the maximum and minimum growth. For stations which lacked ice 

 thickness data, a theoretical curve was constructed from a variation of the 

 Zubov ice growth curve given by the following: 



1.43l2 + 28.61 - 2FDD = 



where I is ice thickness, and FDD is the summation of the cumulative frost 

 degree days in degrees Fahrenheit. An average date for theoretical complete 

 disintegration of the ice was also computed. The period between maximum ice 

 growth and complete disintegration of the ice for each station was based 

 upon available ice information. Initial ice growth and rate of disintegra- 

 tion for the empirical and several theoretical ice growth curves were esti- 

 mated and are indicated by broken lines in the figures. The sparsity of 

 freezeup and breakup data at the individual stations made this estimation 

 necessary. 



III. HARBOR BREAKUP AM) FREEZEUP DATES 



Harbor freezeup data were compiled for the 39 arctic and subarctic 

 stations listed in table 2. Breakup data were sufficient for only 30 

 stations. The data for each particular station were divided into three 

 main categories based on calendar dates. These categories consisted of 

 earliest, latest, and average dates of breakup or freezeup. Freezeup is 

 defined as the date of initial ice formation. Breakup is the date when 



