Drifting Buoys 



Results 



SLAR 



In both phases, four satellite- 

 tracked drifting buoys, each with a 

 2m X 10m window-shade drogue 

 centered at 58m, were used to 

 measure the currents. Tracked by 

 System ARGOS, they provided 8- 

 10 fixes (unevenly spaced in time) 

 each day with a position accuracy 

 of approximately 300m. The 

 ARGOS system is described in 

 detail by Bessis (1981). In addi- 

 tion to position, each buoy meas- 

 ured sea surface temperature at a 

 depth of approximately 1m. Allot 

 the recovered buoys still had their 

 drogues attached. 



In the first phase, one buoy was 

 deployed from an aircraft in the 

 Labrador Current in Flemish Pass 

 (47°N 47°20'W) and three were 

 deployed by ship along the first 

 hydrographic line (48°W). All four 

 buoys were recovered after 

 completion of the surveys. 



As part of the second phase, 

 EVERGREEN deployed a buoy in 

 the Labrador Current in Flemish 

 Pass (47°N 47°18"W) enroute to 

 port. The buoy drifted into the 

 study area at approximately the 

 same time that the second hydro- 

 graphic survey began. Three 

 buoys were deployed during the 

 surveys and before returning to 

 port, three of the four buoys were 

 recovered. The remaining buoy 

 was left in the eddy. According to 

 the drogue sensor on the buoy left 

 in the eddy, its drogue remained in 

 place until 7 July 1986. 



This section is divided into two 

 parts. The first describes the 

 SLAR imagery, with emphasis on 

 the similarities and differences 

 among the four surveys. Because 

 some of the features on the SLAR 

 film are difficult to reproduce 

 photographically, the data are 

 presented primarily in the form of 

 digitized interpretations of the 

 images. The second section 

 compares the imagery with 

 oceanic data that are derived 

 from the hydrographic surveys 

 and buoy tracks. 



Figure C-6, a photomosaic of the 

 26 April SLAR survey, shows what 

 we interpret as the NAC, appear- 

 ing as a dark region along the 

 southern and eastern edge of the 

 image. This is a negative image, 

 thus the dark area represents high 

 radar return. The area of the 

 hydrographic study, enclosed by a 

 box, is dominated by a sharply 

 defined front that tends in the 

 east-west direction. It appears to 

 be the northern edge of a NAC 

 meander or a newly-formed eddy 

 that is interacting with the NAC. 

 The SLAR imagery recorded 

 changes in the shape and loca- 

 tion of this feature over the 

 subsequent three weeks (Figure 

 C-7). In the following discussions 

 this feature will be referred to as 

 an eddy although the SLAR 

 imagery is inconclusive. In no 

 case was it possible to define all of 

 the eddy boundaries because 

 portions could not be located with 

 certainty. In the cases when 

 overlapping imagery permitted two 

 determinations of sections of the 

 eddy boundary , the positions 

 agreed to about 5 km. 



Although the tone of the images 

 varied from survey to survey, the 

 feature mapped in Figure C-7 was 

 always characterized by greater 

 radar return than the surrounding 

 water. This is similar to the finding 

 of Lichy etal. (1981), who found 

 that within a warm core ring there 

 was a more intense radar return 

 than from the surrounding area; 

 however, the differences were not 

 as great as in the present SLAR 

 data. Lichy et al. (1981) also 



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