rougli forecast of survivors expected to reach 48° N. with normal 

 weather conditions for the ensuing months. As the weather condi- 

 tions are monitored each month for the areas to which the crop has 

 progressed, the forecast can be refined. The late February or early 

 March census would enable a more accurate forecast and would enable 

 precise determination of the progress of the berg potential, as well as 

 establish more data and more facts about icebergs. 



In order to help determine the location of the berg potential for the 

 coming ice season, it is necessary to study all available iceberg 

 statistics compiled by the International Ice Patrol over the years. 

 These statistics show that bergs are a threat to shipping on the 

 Grand Banks almost entirely during the 4-month period of March 

 through June. Since 1946, when aircraft were first used by the Ice 

 Patrol for ice surveillance, 94 percent of the total number of bergs 

 drifting south of 48° N. did so during those 4 months, with 64 percent 

 of the total doing so during April and May. Table III shows the 

 approximate dates that the first concentration of icebergs arrived 

 at the Grand Banks and approximate dates when the Grand Banks 

 have become free of icebergs annually since 1946. 



Table III 



' Does not take into account occasional stragglers that might drift onto Grand Banks any month of year. 



Based on a review of annual ice conditions and the data in table III, 

 the following conclusions can be made: 



1. The average date of arrival of bergs on the Grand Banks since 

 1946 is 15 March. 



2. The average date of the end of the ice season since 1946 is 

 1 July. 



3. The Grand Banks iceberg season lasts an average of 3K months. 



4. For the past 18 years of record, the greatest deviations of the 

 length of ice season occurred in 1957 and 1958, with seasons of Q% 

 months and 1 month, respectively. 



5. Ordinarily, bergs which are north of the Grand Banks to perhaps 

 Davis Strait in late June or early July will most likely deteriorate 

 prior to arrival on the Grand Banks due to warming waters. 



6. Prior to the start of an ice season, there is a group of bergs 

 upstream and favorably located for reaching the Grand Banks 



31 



