bergs on the eastern Grand Banks just west of the Current were ex- 

 pected to last for a longer period of time. Although the predominant 

 surface winds were the main factor in the distribution of bergs at the 

 end of April with the Labrador Current and branches a secondary 

 factor, the bottom topography of the Grand Banks also played an 

 important role. While large bergs are able to drift southward in the 

 deeper waters close along the east coast of Avalon Peninsula and along 

 the north and east slopes of the Grand Banks or seaward of them, they 

 do ground along or inside the 100 fathom curve depending upon their 

 draft. A solid dome type berg having a height of 200 feet can be 

 expected to have a draft of about 600 feet based on an average 3/1 

 draft/height ratio. Accordingly, while bergs were being driven along 

 the coast to the south of Cape Race and along the east slope of the 

 Grand Banks regardless of size, only the smaller bergs were able to 

 drift freely southward over the central portion of the Banks while the 

 large bergs were grounding on the northern Grand Banks, and the 

 medium size bergs were able to drift farther south depending on their 

 draft prior to grounding. While the medium and small bergs were 

 permanently removed from the Current in the central portion of the 

 Banks and in relatively warmer waters, an estimated 15 large bergs 

 grounded on the northern Grand Banks were in colder waters and in 

 the vicinity of the Current. These bergs were large enough to last 

 over 6 weeks. 



When the weather pattern would cause a shift to southwesterly 

 winds, the latter bergs were expected to drift back into the south-seek- 

 ing Labrador Current. Therefore, this group remained as a latent po- 

 tential threat to the major shipping lanes near the Tail of the Banks. 

 In addition to the previously mentioned group of 20 bergs in the 

 Current along the east slope of the Grand Banks, there were a few 

 small and medium size bergs on the eastern Grand Banks scattered 

 from 44°30' N. northward and close enough to the Labrador Current 

 to reach it under favorable westerly winds. Some of these bergs were 

 considered large enough to survive to the Tail of the Banks. Although 

 the berg threat was not great in numbers, the abnormally cold water 

 temperatures (see figs. 3 and 4) increased the possibility of bergs reach- 

 ing the Tail and effective Track B. It was noted that the sea surface 

 temperatures cooled in April instead of warming as usual. This 

 was due to a combination of (1) the invasion of very cold water 

 brought down by the Labrador Current from Baffin Bay and Davis 

 Strait which had experienced a very cold winter and (2) the April 

 air temperatures which were about 3° F. below normal for the Grand 

 Banks. An estimated total of 225 bergs drifted south of 48° N. during 

 April. The combined March-April total of 313 bergs south of 48° N. 

 is the highest since 1945, the second heaviest ice year on record. 



15 



