above the sea surface was mea- 

 sured using the altimeter on the he- 

 licopter. 



Table 1 lists the original locations 

 and estimated dimensions of the 

 two icebergs tracked during the 

 study. 



Figure 2 shows the results of the 

 aerial sea ice reconnaissance from 

 the flights made when the TADs 

 were deployed. Both icebergs were 

 in sea ice with concentrations > 9/ 

 10, which consisted of grey ice and 

 medium and thin first year ice. The 

 predominant form was ice cake, 

 whichwas approximately 8/10 snow- 

 covered. 



Reconnaissance 



For two months following the deploy- 

 ments of 4500 and 261 2 onto icebergs, 

 IIP periodically attempted to relocate 

 the icebergs during routine aerial iceberg 

 patrols. Ttie intent was twofold: first, to 

 verify that the TADs were still on the 

 icebergs and, second, to detemiine the 

 extent of sea ice in the vicinity of the 

 icetDergs. On the dates of the flights, the 

 ice observers obtained the most recent 

 satellite-derived TAD positions, usually 

 about 3-6 hours old at flight time. In 

 additon, they reviewed the photographs 

 and video tapes of the icebergs onto 

 which the TADs had t)een deployed. 



Search forthe icebergs on 29 March 



(88) was hampered by low clouds 

 and poor visibility. Asurvey of area 

 with HP's AN/APS-135 Side Looking 

 Airborne Radar (SLAR) showed 

 several icebergs near each of the 

 satellite-determined positions, in 

 neithercase was it possible to identify 

 which iceberg had the TADs. The 

 sea ice cover at both sites , as deter- 

 mined by the SLAR, was approxi- 

 mately 8/10. 



On 8 April (98), twenty-eight days 

 after the TAD deployments, an Ice 

 Patrol flight photographed both 

 TADs, verifying that they were still 

 aboard the icebergs. Although reli- 

 able measurements could not be 

 made, there was little apparent 

 change in the shape or size of the 

 icebergs. The sea ice concentra- 

 tion in the vicinity of each of the 

 icebergs on this date was about 8/10. 



The results of the next attempt, which 

 was made with good visibility on 24 April 

 (114), were not as conclusive. One of 

 the TADs (4500), which was located at 

 50-20 N, 53-03 W, had stopped trans- 

 mitting late on 23 April (113). Near the 

 tocatbn of the last position transmitted, 

 the ice observers saw a bbcky iceberg 

 tfiat had recently broken into two sec- 

 tions, neither of which had the TAD. 

 Severaiothericebergswhichwere within 

 a 20 km radius were examined closely, 

 but the TAD was not tocated. 



At the transmitted position of TAD 



T8bl8 1. Data for LIMEX '89 TAD Deployments onto 

 Icebergs Drifting in Sea Ice 



ARGOS 

 ID 



4500 



2612 



DEPLOYMENT 

 DATE TIME LOCATION 



1 1 MAR (70) 13302 



1 1 MAR (70) ,4002 



51-39N, 53-06W 



51 -49N, 53-08W 



SIZE 



Height X Length 

 (in meters) 



MEDIUM 

 27 m X 1 20 



MEDIUM 

 34 m X 1 00 



2612, an iceberg similar in size and 

 shape to that filmed on 8 April was 

 seen. However, the TAD, which 

 was mostly white, could not be seen 

 on the iceberg. The TAD was not 

 evident on the video tape taken 

 during the flight. Also, it was not 

 possible to identify the iceberg posi- 

 tively because of a narrow field of 

 view of the video tape. However, 

 the ice observers were confident 

 that the iceberg at 261 2's position 

 was the same iceberg as that in the 

 11 March photographs and the 8 

 April video tapes. By 24 April, 

 however, it had developed a large 

 melt pond in its center. Several 

 other icebergs in the vicinity were 

 also examined, but no TAD was 

 sighted. There was no sea ice near 

 either 2612 or 4500. 



During the period 4-1 May two at- 

 tempts were made to search for 

 TAD 261 2, but both were limited by 

 low ceilings and poor horizontal 

 visibility. A thorough radar search of 

 the area around 261 2's reported 

 position on 9 May (48-46.2 N, 49- 

 35.3 W) revealed one radar target 

 that could not be identified with any 

 confidence. There was no sea ice in 

 the vicinity. 



From the flights we conclude that 

 the entire 63-day track of 4500 rep- 

 resents iceberg motion. The si- 

 lencing of its transmitter on 23 April 

 (113) probably was due to a major 

 calving event which crushed the 

 TAD. The only evidence that sup- 

 ports this conclusion is the existence 

 of a large blocky iceberg, recently 

 broken into two pieces, at the last 

 known position of 4500. 



It is likely that 2612 was on its ice- 

 berg on 24 April (114). Although the 

 ice observers did not see the TAD 

 on this date, they were confident that 

 the iceberg closest to the TAD posi- 



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