84 



to indeterminate differential surface drifts of neighboring sea areas, 

 and large ship drifts during periods of darkness and low visibility, 

 cause additional losses. As a matter of fact, a good figure to take for 

 the maximum actual area that can be well covered for ice by one 

 patrol ship per 15-day patrol cruise is 30,000 square sea miles. 



The area about the Grand Banks that most frequently contains 

 bergs and to which it is desirable to confine most of the patrol's 

 activity lies between longitudes 43° and 54° W. and latitudes 40° 30' 

 and 48° N. Deducting the area of the Avalon Peninsula of New- 

 foundland and that of a warm iceless portion in the southeastern 

 corner of this region, it will be found that the total area south of the 

 forty-eighth parallel which is most likely to contain ice contains 

 about 168,000 square geographical miles. Some of the areas over the 

 Grand Banks themselves are not frequented by trans-atlantic traffic. 

 There is, besides, very little sustained current in the shoal water. 

 Therefore, the total area which must be most closely watched can be 

 reduced to about 150,000 square geographical miles. 



North of this great southern ice area and extending eastward for 

 several degrees of longitude from the North American coasts, the 

 waters are particularly liable to be congested with ice. It is normal 

 for unnavigable field ice to exist over broad areas immediately north 

 of the forty-eighth parallel during several winter and spring months. 

 The same waters are liable to be more or less thickly strewn with 

 bergs throughout the whole year. Though ice conditions vary in -dif- 

 ferent localities for various reasons, it is true, generally speaking, that 

 the farther north of the forty-eighth parallel one goes along the 

 North American coast the worse will be the ice conditions met. This 

 holds true all the way up into the Arctic regions that are choked all 

 year round with impenetrable field ice. 



The serious ice conditions likely to be met at any time to the north 

 of the Grand Banks and the forty-eighth parallel are doubtless well 

 realized by the masters of all vessels crossing in the higher latitudes, 

 so for all practical purposes this area can be considered as beyond 

 the ice patrol's particular sphere of action, though not at all beyond 

 its sphere of experience, interest, or knowledge. Ice information 

 received in the form of reports from the northern sections is always 

 placed in the broadcasts and retained for about five days before being 

 dropped. Any vessel requesting special information from the patrol 

 ship regarding ice in the area north of the forty-eighth parallel 

 will usually be able to get valuable information. 



There have been occasional reports of bergs to the west, south, 

 and east of the usual ice area between 43° W. to 54° W. and 40° 

 30' N. to 48° N. Ice in such locations, however, may be considered 

 as due to extraordinary berg or current conditions. The ice-patrol 

 ships themselves can not attempt to locate ice in waters where it is 



