S/'W 55 



50 



45 



40 J9U 



45 - 



40N 



Grand Banks 



• 50 



:>^^ 



52N 



45 



i + 4 ON 



57W 



55 



50 



45 



40 3qw 



Figure B-la Drift trajectories of buoys 4543 and 4549, marked with Julian dates. 



4557 



Buoy 4557 was deployed in a 

 warm core eddy (45°10.2'N 

 47°18.8'W (Figure B-1b)) on 12 

 May 1986 (132) from USCGC EV- 

 ERGREEN as part of an oceano- 

 graphic study. It remained in tfie 

 eddy for three revolutions as the 

 eddy migrated to the east at atxjut 

 4 km/day until 7 June (158). 

 Based on the buoy track, the 

 average diameter of the eddy was 

 70 km and within the eddy, drifter 

 4557 averaged 34 cm/s. Except 

 for two short periods, the tempera- 

 ture reported by drifter 4557 was 

 about 12°C while in the eddy. 



In the first, a 24-hour period on 25 

 May, the temperature decreased 

 to about 7°C and then returned to 

 12°C. The drifter motion was not 

 affected, suggesting that the cold 

 water encountered was only a 

 surface feature. During the 

 second, a 48-hour period begin- 

 ning on 30 May, the temperature 

 decreased to about 6°C and then 

 returned to 12°C. The direction of 

 the drifter was apparently unaf- 

 fected but the average speed 

 nearly doubled, to 65 cm/s. 



After leaving the warm core eddy 

 on 7 June (158), 4557 moved 

 eastward until 10 June (161) when 



it entered a cyclonic (cold core) 

 eddy. In a 24 hour period, the 

 temperature dropped from 12°C to 

 7°C. Drifter 4557 maintained its 

 cyclonic motion until 23 June 

 (174), completing two loops in the 

 eddy. While in the cyclonic eddy, 

 4557's speed ranged from 1 1 cm/s 

 to 133 cm/s, averaging 76 cm/s. 

 Between 19 June (170) and 23 

 June (174), the temperature again 

 rose to 12°C but the rtKition of the 

 drifter did not change. The motion 

 of 4557 between 23 June and 26 

 June (177) -was very sluggish with 

 velocities averaging 12 cm/s and 

 inconsistent direction. On 26 

 June, the temperature increased 



47 



