do drift into areas not surveyed by the Oceanographic Vessel. As a 

 matter of fact, in 1964, at a time when almost 300 bergs were located 

 south of 48° N., over 90 percent of them were out of the survey areas. 

 Frequent ice observations by aircraft and the resulting study of ice 

 conditions have sharply brought into focus the very important role 

 played by wind in helping to determine ice conditions. 



Table IX. Deterioration Time in Days for Bergs 



Note 



1. For tabular type: Small bergs less than 20' high, medium 20'-50', large, greater than 50'. 



2. Dependent upon shape, the deterioration time can be a few days longer for solid types and a few days 

 shorter for drydocls; and badly weathered pmnacled types. 



3. Based on average state of sea during April-May on Grand Banks. Abnormally calm periods will 

 increase the deterioration time while abnormal cyclonic activity will decrease same. 



As mentioned before, a forecast of ice conditions must account for 

 deterioration of ice as well as ice movement. There are no existing 

 reliable quantitative relationships developed between the deteriora- 

 tion of ice and factors causing it. It is believed that the two main 

 factors to be considered are the average water temperature and the 

 state of the sea. If an iceberg is enveloped by pack ice, deterioration 

 is insignificant. A crude table for berg deterioration time has been 

 developed the past 3 years based on aerial observation and sea water 

 isotherm charts. See table IX. Considerable research on iceberg 

 deterioration is required to determine the importance of the various 

 factors and to develop useful relationships for deterioration rates of 

 different shaped and sized bergs at various average temperatures 

 and sea conditions. The replacement of the Patrol Vessel by air- 

 craft as the primary medium for ice observation has resulted in the 

 loss of the intimate and continuous contact the Ice Patrol Vessel 

 maintained with icebergs. Alas, we obtain only a fleeting glance at 

 an iceberg every few days and often we are not sure of its identity. 

 If true understanding of icebergs is to be developed a close and con- 

 tinuous surveillance of individual bergs must be included. This sur- 

 veilance must be accompanied by a scientific program of data 

 collection and analysis so that the drift and deterioration of an ice- 

 berg and the factors affecting same can better be understood. 



If studies of ice conditions and the ice environment on the Grand 

 Banks and vicinity are to be meaningful, ice conditions must be ob- 

 served upstream occasionally. It is necessary that the capability be 

 developed to accurately forecast what will happen to ice that makes the 



98 



