DISCUSSION 



©F IGE AND I 

 GQNDmON' 



:NVmONMENTAL 



Since more than 1 0,000 

 icebergs are calved by 

 Greenland's glaciers into the 

 Baffin Bay each year (Knutson 

 and Neill, 1978), annual fluc- 

 tuations in the generation of 

 Arctic icebergs are not a sig- 

 nificant factor influencing the 

 number of icebergs passing 

 south of 48° N annually. 

 Rather than the supply of ice- 

 bergs available to drift south 

 to the vicinity of the Grand 

 Banks, the factors that most 

 determine the number of ice- 

 bergs passing south of 48° N 

 each season are those affect- 

 ing iceberg transport (cur- 

 rents, winds, and sea ice) and 

 the rate of iceberg deteriora- 

 tion (wave action, sea sur- 

 face temperature, and sea 

 ice). 



The wind direction along 

 the Labrador and Newfound- 

 land coasts can affect the ice- 

 berg severity of each ice year 

 since the mean wind flow can 

 influence iceberg drift. De- 

 pendent upon wind intensity 

 andduration, icebergs can be 

 accelerated along or driven 

 out of the main flow of the 

 Labrador Current (Figure 2). 

 Departure from the Labrador 

 Current normally slows their 

 southerly drift and, in many 

 cases, speeds up their rate of 

 deterioration. 



The wind direction and 

 air temperature indirectly af- 



fect the iceberg severity of 

 each ice year by influencing 

 the extent of sea ice. Sea ice 

 protects the icebergs from 

 wave action, the major agent 

 of iceberg deterioration. If 

 the air temperature and wind 

 direction are favorable forthe 

 sea ice to extend to the south 

 and over the Grand Banks of 

 Newfoundland, the icebergs 

 will be protected longer as 

 they drift south. When the 

 sea ice retreats in the spring, 

 large numbers of icebergswill 

 be left behind on the Grand 

 Banks. Also, if the time of sea 

 ice retreat is delayed by be- 

 low normal air temperatures, 

 the icebergs will be protected 

 longer, and a longerthan nor- 

 mal ice season can be ex- 

 pected. The opposite is true 

 if the southerly sea ice extent 

 is minimal, or if above normal 

 air temperatures cause an 

 early retreat of sea ice from 

 the Grand Banks. 



Sea ice also acts to im- 

 pede the transport of icebergs 

 by winds and currents. The 

 degree to which an iceberg's 

 drift is affected depends on 

 the concentration of the sea 

 ice and the size of the ice- 

 berg. Thegreatertheseaice 

 concentration the greaterthe 

 affect on iceberg drift. The 

 larger the iceberg the less 

 affected its drift is by sea ice. 

 Although it slows current and 

 wind transport of icebergs. 



sea ice is itself an active me- 

 dium, continually moving to- 

 ward the ice edge where melt 

 occurs. Icebergs in sea ice 

 will eventually reach open wa- 

 ter unless grounded. The 

 melting of sea ice is affected 

 by snow cover (which slows 

 melting) and air and sea wa- 

 ter temperatures. As sea ice 

 melt accelerates in the spring 

 and early summer, trapped 

 icebergs are rapidly released 

 and then become subject to 

 normal transport and deterio- 

 ration. 



The Labrador Current, 

 aided by northwesterly winds 

 in winter, is the main mecha- 

 nism transporting icebergs 

 south to the Grand Banks. In 

 addition to transporting ice- 

 bergs south, the relatively cold 

 waterof the LabradorCurrent 

 keeps the deterioration of ice- 

 bergs in transit to a minimum. 



The following discussion 

 summarizes environmental, 

 sea ice, and iceberg condi- 

 tions along the Labrador and 

 Newfoundland coasts and on 

 the Grand Banks of New- 

 foundland for the 1991 ice 

 year. The sea ice information 

 was derived from the Thirty 

 Day Ice Forecast for North- 

 ern Canadian Waters pub- 

 lished monthly by Ice Centre 

 Ottawa, Atmospheric Envi- 

 ronment Service (AES) of 



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