Discussion of Iceberg and Environmental Conditions 



There are a number of factors which affect 

 the number of icebergs that will reach the 

 Grand Banks during a particular ice season. 

 These include the number of bergs that calve 

 from glaciers each year, the ocean currents car- 

 rying these bergs south along the Labrador and 

 Newfoundland coasts, the winds which help to 

 move these bergs, the sea ice which tends to 

 retard the movement of bergs and protect those 

 trapped within its limits, and the environmental 

 conditions which affect the melt rates of the 

 bergs (air and sea surface temperature, storm 

 activity, etc.). Each of these factors has some 

 effect on the extent of the iceberg season off 

 Newfoundland. 



The 1983 Ice Patrol season was the third 

 heaviest season on record with an estimated 

 1352 icebergs drifting south of 48°N. This was 

 considerably more than the 1900-1983 annual 

 average of 381, though less than the maximum 

 number of 1587, recorded during the 1972 

 season. 



Each year thousands of icebergs calve from 

 the glaciers on Greenland's west coast, pro- 

 viding a more than ample supply of bergs in 

 Baffin Bay. The fluctuation in this number of 

 bergs is generally considered to be a minor fac- 

 tor in the number of bergs reaching the Grand 

 Banks because the winds must be favorable to 

 drift the icebergs south and the sea ice must be 

 present to protect them during their long 

 journey. Therefore, International Ice Patrol did 

 not fly any pre-season patrols north of 53 °N in 

 1983. 



The air temperatures (Table 4) have been 

 compared with the heavy sea ice conditions ex- 

 perienced during the 1983 Ice Patrol season. 

 Other environmental factors (winds and at- 

 mospheric pressures) are discussed in this sec- 

 tion in an attempt to explain the large number 

 of icebergs this season. The Oceanographic 

 Conditions section (Appendix B) examines 

 some of the features of the Labrador and North 

 Atlantic Currents that the Ice Patrol observed 

 during the 1983 season. 



Figures 27 through 34 depict the sea surface 

 pressure patterns for January through August 

 1983 and the normal patterns for those months. 

 When interpreting these figures, the isobars, 



drawn as heavy solid lines, are used to deter- 

 mine an average wind direction. Winds tend to 

 blow parallel with the isobars, counter- 

 clockwise around low pressure cells in nor- 

 thern latitudes. 



The predominant characteristic of the 

 monthly average sea surface pressures was the 

 meandering Icelandic Low. The January posi- 

 tion of the low was located northeast of its nor- 

 mal position and was more intense than normal 

 (Figure 27). This produced a southwesterly 

 wind flow over east Newfoundland waters 

 which helped to slow the progress of sea ice in 

 that area. Farther north, the predominant winds 

 were from the north, producing rapid growth of 

 the ice in Davis Strait and off the northern 

 Labrador Coast (see Figure 4). This low shifted 

 south in February (Figure 28), 

 bringing northerly winds which allowed the 

 pack ice to surge southward as illustrated in 

 Figure 5. The Icelandic Low moved back to the 

 northeast again in March (Figure 29), where it 

 was much deeper than normal, as experienced 

 during the 1972 Ice Patrol season, the heaviest 

 on record. This brought westerly winds along 

 the shores of Newfoundland and northerly 

 winds off Labrador, moving the ice south and 

 offshore (compare Figures 6 and 7). It also 

 released some of the icebergs trapped in the 

 sea ice, helping to account for the increase in 

 berg sightings during the early part of April (see 

 Figure 17). The low moved east of Iceland dur- 

 ing April (Figure 30) and remained there 

 through May (Figure 31). This produced 

 predominantly southeasterly winds over the 

 Grand Banks during April and westerly winds in 

 May which aided in sea ice melt and disintegra- 

 tion (see Figures 7 and 8) and caused the 

 icebergs to move further eastward (see Figures 

 18 and 19). The Icelandic Low moved westward 

 in June (Figure 32), centering itself near 

 southern Greenland. It remained in this area 

 through July (Figure 33) and August (Figure 34). 

 The southerly winds produced by this weather 

 system brought warm water (as described in 

 Appendix B) up through the Grand Banks, 

 pushing the sea ice and iceberg limits slowly 

 northward as illustrated in Figures 22 through 

 25. 



37 



