1987 DATA COLLECTION 

 EFFORT 



This study collected data on six 

 medium to small icebergs for a 

 period ranging from 2.1 to 6.3 

 days. The icebergs were studied 

 as they drifted south with the 

 Labrador Current on the northeast 

 Newfoundland Shelf (centered 

 around position 50-45°N, 53- 

 30° W); see Figure E-2. The study 

 was conducted between 15 and 

 21 June 1987 using the USCGC 

 TAMAROA, a 68m (205 ft) U. S. 

 Coast Guard cutter. 



Iceberg above water dimensions 

 were taken during daylight using a 

 camera and reticulated laser 

 rangefinder. Iceberg shape and 

 size were calculated from photo- 

 graphic images scaled according 

 to rangefinder measurements. 

 This required a 360 degree look at 

 each iceberg; measuring and 

 photographing all prominent faces. 

 Measurements were accurate to 

 +/- 8% of the observed dimen- 

 sions. No underwater iceberg 

 dimensions were measured. 



The rangefinder-derived distances 

 were used with visual bearings to 

 fix the icebergs' positions during 

 daylight. At night, radar bearings 

 and ranges were used. The cutter 

 used LORAN-C and SATNAV to 

 fix its position. Positional accu- 

 racy for iceberg positions was esti- 

 mated (by summing system 

 errors) to be +/- 750m. Table E-1 

 summarizes the observed dimen- 

 sions and estimated drift of the 

 icebergs. 



Hourly environmental observations 

 included: air and sea surface 

 temperature, cloud cover, and 

 wind (at 22.3m). Sea surface 

 temperature was taken by bucket 

 thermometer (error was +/- 0.1°C); 

 wind was measured by the ship's 

 anemometer. Wave height, period 

 and direction were visually esti- 

 mated every six hours. Visual 

 wave observations were estimated 

 to have an error of +/- 0.5m for 

 wave height; and +/- 2sec for 

 period. Surface currents were 

 inferred from the drift of two 



satellite-tracked drifters (FGGE- 

 hulled), which had window-shade 

 (2m X 1 0m) drogues. Both drifters 

 were deployed at the same time 

 near the center of the cluster. 

 One was drogued near the surface 

 (center of the drogue: 8m deep), 

 while the other was drogued at 

 58m, at the core of the Labrador 

 Current. Temperature vs. depth 

 profiles were taken in the vicinity 

 of each iceberg and transects 

 were made at the beginning and 

 end of the study to determine 

 iceberg drift in relation to the 



57° 56° 55° 54° 53° 52° 51° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41° 40° 39' 

 52°: 



38 



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:51° 

 150° 



48° 



47° 



46° 



E45° 



j44° 



:43° 



42° 



41° 



40° 



E39° 



- denotes the mean position of the Labrador Current 



- defines the June 1 987 study area 



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57° 56° 55° 54° 53° 52° 51° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41° 40° 39 



38° 



Figure E-2. International Ice Patrol Study Area. This figure depicts the 

 area in which iceberg drift and deterioration is operationally modelled by 

 IIP. The 200m bathymetric contour is shown to describe the Grand 

 Banks of Newfoundland and Flemish Cap. 



111 



