BUOY DEPLOYMENT 

 STRATEGY 



A recent study (FENCO,1987), 

 sponsored by the AES, devised 

 strategies for the optimum deploy- 

 ment strategy for drifting buoys 

 used to derive oceanic currents for 

 iceberg drift forecasting. This 

 study focused on Canadian 

 domestic iceberg interests, that is, 

 on regions where offshore oil 

 exploration is taking place (the 

 slope and shelf east of Newfound- 

 land and Labrador). Although the 

 area of Ice Patrol operations 

 extends far to the south of this 

 region, many of the study results 

 apply directly to the IIP mission. 



The study showed that, even for a 

 small portion of the region (250 km 

 X 250 km), at least 400 buoys 

 would be required to resolve the 

 eddy field throughout the iceberg 

 season. Ice Patrol's operations 

 area is many times this size. The 

 costs associated with deploying 

 and tracking many hundreds of 

 buoys far exceeds the entire Ice 

 Patrol budget. Thus, such cover- 

 age is impractical. 



Ice Patrol's buoy deployment 

 strategy focuses on the current 

 that is the major conduit of ice- 

 bergs into the North Atlantic 

 shipping lanes, the southward- 

 flowing off-shore branch of the 

 Labrador Current. The goal is to 

 monitor this current for the entire 

 season by keeping one or two 

 buoys in it at all times. 



Several of the study's conclusions 

 and recommendations support Ice 

 Patrol's recent deployment 

 strategies with the intent of gaining 

 the most benefit from a few buoys. 

 A fundamental conclusion of the 

 study is to deploy buoys as far 

 north (north of 50°N) as possible 

 because the southward mean flow 

 of the Labrador Current will carry 

 the buoys into the southern areas 

 of interest. Ice Patrol's experience 

 has shown that this approach is 

 reasonable with two important 

 limitations. The first is that early in 

 the iceberg season (March and 

 April) the buoys should not be de- 

 ployed in areas with significant 

 concentrations of sea ice ( > 3/10) 

 so that wind-driven movement of 

 the sea ice will not contaminate 

 the drifter data. Second, in many 

 cases buoys deployed from 50 - 

 52°N move eastward to the north 

 of Flemish Cap, and hence do not 

 enter the region south of Flemish 

 Pass. Because Ice Patrol requires 

 drift data in this area, it is fre- 

 quently necessary to deploy buoys 

 directly in the pass to ensure that 

 the buoy will move to the south. In 

 this case the buoys are deployed 

 at 47°N between 46-30°W and 47- 

 30°W. 



The study recommends against 

 releasing a buoy beside a particu- 

 lar iceberg because, in a period of 

 a few days, the buoy and the 

 iceberg are likely to be separated 

 by distances larger than the typical 



eddy scales. This is a sound rec- 

 ommendation. Ice Patrol deploys 

 buoys near drifting icebergs only 

 for specific iceberg drift studies, 

 not for operations. 



Finally, the study recommends a 

 thorough review of the Ice Patrol 

 mean current file and the inclusion 

 of data on the variability of the 

 current. Ice Patrol has begun 

 such a review and is using drift 

 tracks collected since the begin- 

 ning of the buoy program (1976) to 

 improve the mean current data. 



AIRCRAFT DEPLOYMENTS 



Ice Patrol has deployed satellite- 

 tracked buoys from HC-130's 

 since 1979. The buoy is strapped 

 into an air-deployment package 

 and launched out the rear door of 

 an HC-130 flying at an altitude of 

 500 feet (150 m) at 150 knots (77 

 m/s). The air-deployment pack- 

 age consists of a wooden pallet 

 and a parachute, both of which 

 separate from the buoy after it 

 enters the water. The parachute 

 riser is cut by a cable-cutter that is 

 activated by a battery that ener- 

 gizes when immersed in salt 

 water. The pallet separates when 

 salt tablets dissolve and release 

 straps holding the buoy to the 

 pallet. The buoy then floats free 

 and the drogue falls free and 

 unfurls. 



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