APPENDIX B 



INTERNATIONAL ICE 

 PATROL'S 1989 

 DRIFTING BUOY 



PROGRAM 



MICHAEL B. CHRISTIAN 

 DONALD L. MURPHY 



INTRODUCTION 



The 1989 iceberg season was the 

 fourteenth consecutive yearthat the 

 International Ice Patrol (IIP) used 

 satellite-tracked buoys to measure 

 currents in its operations area in the 

 western North Atlantic Ocean. The 

 buoy trajectories are used to provide 

 near realtime current data to the Ice 

 Patrol iceberg drift model. The 

 currents derived from the buoy tra- 

 jectories are used to modify the mean 

 currents temporarily in the region 

 through which the buoy is moving. 

 Shortly after a buoy departs the re- 

 gion, the current is reverted to its 

 mean value (Summy and Anderson, 

 1983). 



During 1 989 Ice Patrol deployed nine 

 satellite tracked buoys (Table B-1). 

 Three of the buoys deployed in 1 989 

 eventually beached in Europe. 



Table B-1 



BUOY DEPLOYMENT 

 STRATEGY 



Monitoring the currents with drifting 

 buoys in the entire Ice Patrol op- 

 erations area (40N to 52N; 39W to 

 57W) for the entire iceberg season 

 is impractical. A recent study 

 (FENCO, 1987),fundedbyCanada's 

 Atmospheric Environment Service, 

 showed that at least 400 buoys per 

 year would be required to resolve 

 the eddy field in a 250-km by 250- 

 km area, a small fraction of MP's 

 area of responsibility. 



Ice Patrol's buoy deployment 

 strategy focuses on the Labrador 

 Current. The southward-flowing off- 

 shore branch of the Labrador Current 

 is the major conduit of icebergs into 

 the North Atlantic shipping lanes. 

 IIP monitors this current by keeping 

 one or two buoys drifting in it 

 throughout the iceberg season. 



Buoys are deployed as far north 

 (north of 50N) as possible because 

 the southward mean flow of the La- 

 brador Current carries 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 



Summary of 1989 Deployments 



The standard configuration for the 

 operational buoys was a 3-m long 

 spar hull with a 1 m diameter flota- 

 tion collar. Each buoy was equipped 

 with a 2-m by 10-m window-shade 

 drogue attached to the buoy with a 

 50 m tether of 1/2 in (1.3 cm) nylon. 

 The center of the drogue was at a 

 nominal depth of 58 m. Each buoy 

 had a temperature sensor (accurate 

 to approximately 1°C) mounted ap- 

 proximately 1 m below the water- 

 line, a drogue tension monitor, and a 

 battery voltage monitor. Three of 

 the buoys deployed during 1989 

 (9875, 9876, and 9879) were 

 equipped with barometric pressure 

 sensors funded by the U. S. Navy. 



The data from the buoys are ac- 

 quired and processed by Service 

 ARGOS. Ice Patrol queries the 

 ARGOS data files and stores the 

 buoy data once daily. Most of the 

 buoy position data fall within the 

 standard accuracy provided by Ser- 

 vice ARGOS (--350 m). All of the 

 buoy data were entered onto the 

 Global Telecommunications System 

 (GTS). Each buoy, except 9876, 

 was assigned a World Meteorologi- 

 cal Organization (WMO) number. 



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