current followed the bottom topography around 

 the sharp beak-like feature near 48°N, 47°W. 

 However, the drift of a BTT buoy through this area 

 suggests that the water motions did not follow this 

 bathymetric feature. The flow of water off of the 

 Grand Banks at 46°N indicated in the dynamic 

 topography, while possibly real, is likely a result of 

 the sampling methods. 



A joint project with Woods Hole Oceanographic 

 Institution (WHOI) was conducted during the 1978 

 HP season. WHOI supplied two BTT buoys of the 

 type manufactured by Polar Research Labs, Inc., 

 Santa Barbara, California. Details of this buoy are 

 covered in CG-188-31. Both buoys were deployed 

 by the CGC EVERGREEN (WAGO 295) in the Ice 

 Patrol area. They contained battery voltage 

 monitors, sea surface temperature sensors, and 

 drogue tension monitors. Nylon line, IV2 inches in 

 diameter and weighted at the bottom end with 50 

 pounds of chain, was used to increase water drag. 



The first buoy, platform I.D. 264, was deployed 

 in the North Atlantic Current at 0625 (GMT) on 5 

 April at 42°-39.5'N, 45°-28.0'W. The deployment 

 criterion was that the buoy should be deployed in 

 the area of steeply sloping isotherms east of the 

 Grand Banks where the 10° isotherm is at a depth 

 of 200-300 meters. Before the CGC 

 EVERGREEN reached the area it was thought 

 that the deployment criterion would be found near 

 42°-44'N, 42°-48'W. However, an XBT survey 

 found the North Atlantic Current much further to 

 the west. 



A plot of the buoy's trajectory is shown in figure 

 2A. By 1323 (GMT) 9 July this buoy had drifted 

 eastward to 40°47'N, 39°13'W. This position is 

 well to the east of the IIP area and data collected 

 after that time have no direct application to IIP 

 operations. Buoy drifts such as these show that the 

 currents in this area are not as straightforward as 

 once thought. Although this is a preliminary 

 report, it should be noted that currents as far north 

 as 44 °N are not totally independent of currents as 

 far south as 39°N. The second buoy, platform I.D. 

 731, was deployed in the Labrador Current along 

 standard section AlB at 1317 (GMT) on 13 April in 

 position 48°-33.7'N, 49°-02.4'W. The deployment 

 criterion for this buoy was to place it in the 

 Labrador Current along the 500m contour. A plot 

 of this buoy's track through June 27th is shown in 

 figure 3A. 



The first significant feature is the buoy's general 

 track down along the eastern edge of the Grand 

 Banks. At the time of deployment it was not 

 known whether the buoy would go south through 

 Flemish Pass or head east, north of Flemish Cap. 

 Because this information is critical in iceberg drift, 

 work will continue with drift models that can 

 account for a drift object's motion north and west 

 of Flemish Cap. 



A second feature of the buoy's trajectory that is 

 important to IIP is the smaller scale motions that 

 can be seen along the trackline at about 

 47°-23'N,45°-42'N, and again at 42°-50'N. These 

 motions cannot be explained by looking at the 

 dynamic topography. Although the buoy returns to 

 a course predicted by the dynamic topography, it 

 ends up being miles north of where it would have 

 been had it not made these excursions. Prehminary 

 analysis of wind generated currents also indicate 

 that they cannot explain what is observed. 

 Whatever the forces are that cause these motions, 

 they may contribute significantly to the errors in 

 any drift prediction model if they are not included. 



Another area of large uncertainty in drift predic- 

 tion is near 44°-50'N, 48°-20'W. It is in this area 

 that the normal dynamic topography shows the 

 Labrador Current as two branches (Scobie and 

 Schultz, 1976). The main branch of the Labrador 

 Current continues south along the Grand Banks. 

 The other section travels in a northeasterly direc- 

 tion. If drift objects travel south through Flemish 

 Pass it is not known which branch of the Labrador 

 Current they will follow. In 1976 the BTT buoy, 

 platform I.D. 0177, was deployed along standard 

 section A2 in the Labrador Current (Super and 



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