pared with the pressure gradients computed from data obtained from 

 Normal Weather Maps Northern Hemisphere Sea Level Pressure 

 published by the United States Weather Bureau. To correlate these 

 gradients with ice movements, wind vectors were drawn 15° to the 

 right of the geostropic wind to approximate the relations between ice 

 ch'ift, wind direction and coriolis' acceleration. After these vectors 

 were drawn, departures from normal conditions were noted for the 

 1950 season. The average velocity of the winds in February was 

 greater than the normal wind for this month. This increase in ve- 

 locity was accompanied by an early movement of bergs to the Tail of 

 the Grand Banks and a movement of pack ice in late February into 

 the northern part of the Grand Banks area. The average wind for 

 March had a greater velocity than normal. Drift ice in this month 

 covered the northern half of the Grand Banks and reached its maxi- 

 mum southerly limits for the season. The greatest departure from 

 normal conditions occurred in April when the average wind was south- 

 southwesterly rather than northwesterly. This opposed the move- 

 ment of drift ice southward and tended to force drift ice into warmer 

 water north of the Grand Banks. By the end of April the Grand 

 Banks area south of 48° N., was clear of drift ice. Usually drift ice 

 reaches its maximum southerly limits in this month. Normal vectors 

 and average vectors for the 1950 season are shown in figure 15. 



Wind has a greater and more direct effect on drift ice than on bergs. 

 In the latter case wind does not directly affect the movement of a berg 

 until it has a relatively shallow draft. However, it indirectly affects 

 the movement of bergs by creating a wind-driven current in water 

 which becomes deeper and consequently more effective in transporting 

 bergs the longer a wind blows from a certain direction. In February 

 and March normal winds blow in a direction which aids the movement 

 of drift ice to the southeast both by exerting a stress on the ice and 

 also adding energy to the existing current system. The average 

 vectors for February and March show velocities greater than the 

 normal vectors. The net result of these greater velocities was an 

 early movement of pack ice southward, and consequetnly early de- 

 struction of the 1950 crop of drift ice. This destruction was hastened 

 by the average wind in April which blew against the current system 

 and tended to force the drift ice into warmer water north of the 

 Grand Banks. The average calm in May and the early disappearance 

 of drift ice allowed many bergs which would otherwise have drifted 

 to the eastern edge of the Grand Banks to enter Notre Dame Bay and 

 ground along the Newfoundland Coast. Movement of bergs to the 

 east of Flemish Cap in this month was the result of oceanographic 

 conditions further south rather than the lack of an average wind. 

 June was marked by an average wind that was greater than normal. 

 This contributed to the movement of icebergs into the area in July 

 after the ice season had been terminated. 



22 



