^3' 





^^:>> 



Figure 21.-Transect Ill-Section 18, June 3, 1963. (See caption for fig. 13.) 



vected along the boundary or formed locally by 

 occlusion of a lateral tongue of warmer bound- 

 ary water. 



About 7 hours later was the next crossing of 

 the boundary (fig. 7). The boundary disturb- 

 ance, which had just started in the previous 

 section, had intensified and looked like a shal- 

 low small-scale upwelling with a cool belt very 

 close to the Gulf Stream water. The surface 

 temperature trace shows it as a cool-water 

 stripe. The mass of 12- C. water in the sub- 

 surface has reduced further in volume. The 

 warm bubble is at a shallower depth in this 

 section than in the previous and is somewhat 

 warmer. It may be either a new feature or a 

 slow drifting of the same occluded warm water 

 along the boundary. We could expect such an 

 elongated bubble to be warmer in the center. 



In the following section (fig. 8) about 5 

 hours later, a very large-scale process begins 

 within the left side of the Gulf Stream. The 

 former boundary is at about the same location, 

 and the small-scale disturbance is still clearly 

 marked on the surface temperature trace. A 



new boundary is forming 25 miles (46.3 km.) 

 within the Gulf Stream near the velocity maxi- 

 mum. The cool belt at the surface is shown at 

 the right section of the temperature record at 

 BT number 65. The surface salinity in the cool 

 stripe is 36.04 "Im and, probably, is somewhat 

 lower in its center. To the left and to the right 

 of the cool band the surface salinities are 

 36.37 "/(Ml and 36.37 "/„n. The bottom of the mixed 

 layer is indicated by the dashed line. The cool 

 band has no mixed layer. Apparently an intense 

 upwelling process has been just started and is 

 cutting off a very large portion of the Gulf 

 Stream water from the main body of the 

 Stream. 



The next section shown in figure 9 was made 

 about 20 hours later. The intermediate zone is 

 about 35 miles (64.8 km.) wide and is at about 

 the same stage of development as it was in the 

 first section (fig. 3). The separated mass at the 

 Gulf Stream is split into two shallow warm- 

 water cores. The subsurface has changing jets 

 or tongues of cold and warm water immediately 



408 



U.S. FISH AND WILDLIFE SERVICE 



