WATER CIRCULATION 



The mean Eulerian current (that is, current measured at a fixed point) 

 was southwestward on the shelf adjacent to Lydonia Canyon and above the level 

 of the canyon rim at speeds of 5 to 10 cm/s. This southwestward flow parallel 

 to the isobaths is consistent with previous descriptions of the mean 

 circulation on Georges Bank. 



On the continental slope, mean flow was strongly influenced by Gulf 

 Stream warm-core rings (Figure 3). Several rings passed to the south of 

 Lydonia Canyon during the observation period; the strong clockwise flow around 

 them caused eastward flow along the edge of the shelf as strong as 80 cm/s. 

 There is some evidence that the warm-core rings affect flow in the canyon by. 

 generating packets of high frequency current fluctuations. On the slope, the 

 influence of the rings in the water column extended to at least 250 m, but not 

 to 500 m. The influence of the rings did not extend onto the continental 

 shelf in water depths of 125 m. 



Over the slope, there was a persistent off-shelf and down-slope component 

 of flow near the bottom of a few centimeters per second. Within the canyon, 

 the mean Eulerian flow near the bottom was complex (Figure 4). Near the head 

 of the canyon, at 300 m, net Eulerian flow 5 meters above bottom (mab) was 

 down-canyon at about 3 cm/s and was weak at 50 mab. At 550 m, the near-bottom 

 flow was up-canyon. At 600 m, the near-bottom flow was weakly up-canyon; the 

 flow at 100 mab was down-canyon. These observations suggest a convergence of 

 the mean Eulerian flow between 300 and 600 m and possibly several cells of 

 recirculation along the canyon axis. However, because of the energetic, 

 nonlinear, high-frequency motion observed in the canyon and the small spatial 

 scales, the mean Eulerian current may not indicate the actual Lagrangian 

 water-particle motion. Further analysis is required to determine the 

 Lagrangian circulation pattern. 



Measurements made on the eastern rim of the canyon at about 200 m show 

 westward flow directly across the canyon axis. Measurements on the eastern 



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