ICE & ENVIRONMENTAL CONDITIONS 



September-December 1978 



Figures 1 through 3 illustrate the growth of sea 

 ice during this period. By December ice was as far 

 south as the Strait of Belle Isle and extended 100 

 miles or more off the Labrador Coast. Iceberg 

 sightings during this period were infrequent with 

 Ice Central Ottawa reporting some icebergs in the 

 waters off the Labrador Coast. Figures 20 through 

 23 depict surface pressure characteristics that con- 

 tributed to ice formation and movement. During 

 this period conditions were near normal, with 

 predominately westerly winds and no unusual ice 

 conditions noted. 



January-February 1979 



Ice formation continued as shown in figures 4 

 and 5. By mid-February sea ice extended south as 

 far as Cape Bonavista and out to 50 miles off the 

 coast of Newfoundland. In early February the Ice 

 Patrol conducted the first aerial reconnaissance of 

 the 1979 season. Icebergs were sighted off the 

 Coast of Labrador and by late February icebergs 

 were probably crossing 48°N though there were no 

 reconnaissance flights to verify this until early 

 March. The average surface pressures shown in 

 figures 24 and 25 indicate that a strong northerly 

 flow existed in February creating the ideal condi- 

 tions for moving ice and icebergs south towards 

 the shipping lanes. 



March 1979 



Limited reconnaissance during January and 

 February led to the Ice Patrol conducting a 

 comprehensive survey of the waters off 

 Newfoundland during the first week of March. 

 Icebergs were observed south of 48°N and as a 

 result the Ice Patrol commenced broadcast of ice 

 conditions on 6 March 1979. Figure 13 shows the 

 estimated ice conditions at that time. Sea ice 

 reached its southern limit during this month as 

 seen from figure 6. However, the approaches to 

 the Strait of Belle Isle and St. John's were covered 

 by as much as seven oktas of sea ice. The ice condi- 

 tions for 24 March are shown in figure 14. The 

 average surface pressures for March (figure 26) 



resulted in predominantly westerly air flow which 

 kept the bergs offshore and ensured their clear 

 passage southward. The estimated number of 

 icebergs crossing 48°N for March was 20. 



April 1979 



April marked the beginning of the sea ice retreat 

 and was also the heaviest single month for icebergs 

 crossing 48°N. An estimated 81 bergs drifted 

 south during this month. Some typical ice condi- 

 tions are shown in figures 7 and 15. It was during 

 April that significant changes in weather patterns 

 occurred that led to prevailing onshore breezes and 

 the drift of icebergs out of the Labrador Current 

 and towards the coast. This resulted in fewer bergs 

 reaching the Grand Banks and a reduced hazard to 

 shipping. Figure 27 shows the average surface 

 pressures and the low pressure system east of 

 Newfoundland that dominated the weather for 

 April. 



May 1979 



The unusual weather patterns of April continued 

 to dominate through May. The weak low pressure 

 system was moved east by a ridge of high pressure 

 as seen in Figure 28. The result was a still per- 

 sistent onshore breeze and a corresponding 

 shoreward drift of ice and icebergs. Sea ice condi- 

 tions are shown in figure 8; iceberg conditions for 1 

 May and 31 May are shown in figures 16 and 17. 

 These figures show the trend towards shoreward 

 drift and reduced numbers of icebergs that 

 developed during this month. In May an estimated 

 34 bergs drifted south of 48°N. However, recon- 

 naissance flights north along the coast of Labrador 

 sighted hundreds of icebergs that would have 

 drifted further south if they had not been blown 

 out of the main stream of the Labrador Current. 



June 1979 



By June it was apparent that the iceberg threat 

 to shipping was greatly diminished and that few 

 bergs would drift south towards the Grand Banks. 

 Sea ice drifted no further south than the Labrador 

 Coast and only an estimated nine bergs crossed 



