days ahead of schedule. Shipping using Canadian Track "D" was 

 advised to use the Track "B" turning points, and on this date the USCGC 

 Acushnet was ordered from its home base in 'Portland, Maine, to in- 

 augurate the surface patrol. On 13 March the Acushnet took station 

 by the southernmost known ice, a medium-sized pinnacle berg which by 

 the 17th had drifted to a point midway between the eastbound and 

 westbound lanes of Track "B." 



Field ice conditions over the Grand Banks during the 1957 season 

 were particularly severe and widespread. These conditions are shown 

 graphically in figures 12 to 18 and are described in the monthly ice 

 conditions. Field ice climaxed its greatest southward extent in the 

 early to middle part of March when it reached to latitude 42°25' N. 

 blocking the entire Track "D" and within 50 miles of Track "B" west- 

 bound. Canadian Track "E" remained hampered by field ice until the 

 end of May but Tracks "F" and "G" (Strait of Belle Isle) and the 

 Newfoundland coast were not clear until well into June and July. St. 

 John's Harbor was closed by ice fields for long periods and to such an 

 extent that even a powerful United States Navy icebreaker was unable 

 to force entry for a period of several days. Many fishing and coastwise 

 vessels suffered damage in the pack ice attempting to enter ports. Resi- 

 dents along the Newfoundland coast termed conditions the worst in 

 many years, some going back to 1904. The northeast coast was close- 

 packed with ice long after the usual opening dates. The first vessels 

 reached Botwood, Newfoundland, on 6 June, that port having been 

 blocked for approximately 5 months. 



The initial berg threat to the effective steamer tracks on the Grand 

 Banks subsided early in April, but in mid-May aerial ice reconnaissance 

 revealed numerous bergs in the Labrador Current between latitudes 

 44° N. and 46° N. drifting rapidly southward toward the "Tail-of-the- 

 Banks." This corresponded to a breakup in the field ice farther north. 

 These bergs were destined to drift into Track "B" or the areas immedi- 

 ately adjacent and thereby necessitated an almost continuous surface 

 patrol from 18 May to 13 August. They were also to cause a 24-day 

 deferment of the scheduled northward shift from Track "B" to Track 

 "C." 



The necessity for a rigorous surface patrol required that the oceano- 

 graphic vessel USCGC Evergreen, after two current surveys, be diverted 

 to patrol duty on 23 May. 



Rapid regression of bergs during the middle of July left the Grand 

 Banks area almost ice free. Aerial observation on 20-23 July showed 

 only one berg likely to come south of 46° N. Accordingly, Commander, 

 International Ice Patrol recommended the now postponed shift from 

 Track "B" to Track "C." The North Atlantic Track Agreement 

 Authorities concurred and Track "C" became effective on 24 July. 



The ice hazard on 24 July had reduced to one berg, but due to its large 

 size and rapid drift southward in the still well-developed Labrador 



