71 



occupy positions which are more or less characteristic for the Grand 

 Banks area. It is natural to speculate whether daily synoptic data 

 for the ocean depths would show short-lived movements, similar to 

 those that form in the atmosphere. The ice patrol, however, is 

 almost exclusively concerned in the extent to which major changes, 

 in the circulation cause a deviation in the iceberg drifts. And this, 

 information, we find for all practical purposes, is contained in the 

 current surveys, obtained monthly or bimonthly. 



In carrying on the scientific investigations, the ice patrol follows a 

 program laid down by the ice patrol board which deals with its 

 general policies and plans. First, our principal concern during the 

 particular ice season is tracing the developments in the circulation 

 from March to July, as governing the drift of bergs approaching the 

 southern end of their transit. For example, the observations taken 

 by the patrol in the first part of April, 1927, indicated the scheme of 

 circulation around the Tail of the Bank depicted on Figure 34 p. 75. 

 And the correctness of this picture is evidenced by the fact that on 

 April 10 to 15 a berg drifted southward, swung around the Tail, and 

 stranded in on the Bank, in conformity with the stream lines that 

 had been calculated. In order to be prepared for future bergs in 

 April, a second investigation of the waters was made April 21 to 25, 

 which showed that the general scheme of circulation had slightly 

 altered. (Fig. 38, p. 78.) No more bergs, it happened, drifted so far 

 south as the Tail, but if they had there were data on board which 

 would have been ample to predict their probable paths. Information 

 on the ever-changing positions of the currents, it is plain to see, is of 

 great value to the patrol in conducting its ice service to shipping. 



The other aspect of the oceanographic work is one with a longer 

 view, which, after a few more years' mapping of the currents, sees 

 much information resulting from a comparison of the maps from year 

 to year. We believe that there are particular features which are more 

 or less characteristic of all years; types that are easily subject to 

 classification. Already, for instance, we are convinced, as a result 

 of current data collected even over a short period of years, that an 

 area of approximately 1,000 square miles, located on the southwest 

 slope of the Grand Bank, is normally the seat of an anticlockwise 

 rotating eddy. This phenomenon (and it is important from our 

 viewpoint) explains why bergs passing close by the Tail so often drift 

 inshore and remain to melt in the shoal water on the Bank. There- 

 fore, the greater the number of systematic surveys of the circulation, 

 the better we are able to understand what formerly seemed a chance 

 disposition of the ice. 



There were five dynamic surveys made of the waters of the ice re- 

 gions in 1927. The positions at which observations are usually made 

 (C. G. Bull. No. 15, p. 87) were not adhered to closely in 1927, be- 



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