DISCUSSION OF 1972 ICE CONDITIONS 



Although tlic number of iceberjis which an- 

 nually drift south of 48°N (fi<;. 59) fluctuates 

 considerably, this number generally declined dur- 

 ing the 40 years prior to 1972 (Table 1). In 



Table 1 — Yearly Average Number of the 

 Icebergs South of 48°N 



Years 

 1932-1941 



Average # of Icebergs 

 419.1 



fact, during that entire period, only in 1945 did 

 this number exceed 1000. AVliy then did this 

 trend come to such an abrupt end in 1972? 

 Primarily it was a result of substantial changes 

 in oceanographic and meteorological conditions 

 during late 1971 and early 1972. These condi- 

 tions directly ati'ected the following factors that 

 in turn determine the iceberg count on the Grand 

 Banks : 



• Supply of icebergs 



• Wind 



• Curi'ent 



• Waves/Sea Ice 



• Sea Temperature 



• Air Temperature 



• Precipitation 



Iceberg Supply 



Most of the icebergs which eventually reach 

 the Grand Banks are calved from glaciers along 

 the west coast of (ireenland. Determining the 

 annual iceberg production of these glaciers is a 

 difficult task complicated by tiie remoteness of 

 this vast region. One census will not result in 

 an accurate count as icebergs may survive for 

 several years in the survey area. To obtain an 

 accurate production figure, it is necessary to con- 

 duct several censuses over a period of years while 

 taking into account such factors as melting and 



calving of icebergs. Since such studies have not 

 been undertaken, it is not surprising that esti- 

 mates of annual iceberg production vai-y greatly. 

 Wolford (1972) reports several estimates of ice- 

 berg production ranging from 7,500 to 40,000 

 and suggests that the higher value is more 

 realistic. Using even the most conservative esti- 

 mates, the annual supj)ly of icebergs is substan- 

 tial enough to suppoit heavy ice seasons on the 

 Grand Banks. 



Each year IIP conducts iceberg reconnaissance 

 flights from Newfoundland northward along the 

 Canadian coast to estimate the severity of the 

 upcoming ice season. A January 1972 flight 

 covered the coastal area to Cape Dyer and a 

 February 1972 flight terminated at Cape Chidley. 

 Past experience indicated that only icebergs lo- 

 cated south of these points at these respective 

 months will reach the Grand Banks during the 

 following ice season. The result of these 1972 

 flights was surprisingly low iceberg counts (fig. 

 60). 



This apparent contradiction can be explained. 

 The majority of iceberg drift studies conducted 

 by IIP found icebei'gs advancing southward 3 

 to 6 miles per day. However, in some instances, 

 advances in excess of 20 miles per day have been 

 noted (Wolford, 1972). Under ideal conditions, 

 as was the case in 1972, it is not unreasonable to 

 assume that icebergs can maintain a speed of 

 advance of 0.5 knots over a long period of time. 

 At this rate, icebergs that were in Baffin Bay in 

 January could reach the Grand Banks during 

 the ice season. With the supply of icebei'gs in 

 Bafliin Bay estimated to be more than 40,000 at 

 any one time (Sanderson and Davis, 1972), only 

 a small fraction of these icebergs is neetled to 

 greatly increase the severity of the ice season. 

 This is wliat is believed to have happened in 

 1972. 



Winds 



Icebergs ai'c liansported (o the (irand Banks 

 by a complex combination of wind and current. 



