Earlier discussion of the horizontal analyses revealed changes 

 between phases I and II: the cross sections emphasize these changes. 

 The cross section at 40°N (figure 11, phase II) shows significant 

 changes after two weeks. The subsurface cold feature (E) has drifted 

 about 20 km eastward, while the surface feature (D) (figure 8) indicates 

 a southwestward advance of cold water. From 67°W to 69°W between 50 

 and 100 m, the thermal structure is complex with some cold shelf water 

 (10°C) intruding at this depth. This cold intrusion has created an 

 extensive area of strong sound channels (G). A study of the seasonal 

 variations of this phenomenon has been presented by Cresswell (1967). 

 As previously discussed, the surface cooled by as much as 8°C. Warming 

 is noted at all depths over the eastern half, particularly at 65°W. 

 Many of the same changes occurred along 39°40'N (figure 12, phase II). 

 Warming has occurred to the east and the subsurface cold feature (E) 

 moved eastward about 20 km, but the sound channel region (G) has much 

 less horizontal extent. Southerly movement of the sound channel region 

 is being blocked partly by the deep warm eddy (B) that has moved westward 

 about 20 km. The southern portion of the warm eddy appears along 39°20' 

 (figure 13, phase II). The Gulf Stream wall is south and the warm eddy 

 is north of the cross section along 39°N (figure 14, phase II). The 

 thermal structure along 39°20' is fairly uniform for its position in 

 relationship to the Gulf Stream and Slope Water. The warming evident 

 along the eastern half of the northern sections has diminished consider- 

 ably. 



The cross sections along SS^O 1 , 38°00' , and 37°30'N, figures 15, 

 16, and 17, phase II, respectively, all show the Gulf Stream meander 

 and have similar characteristics. They differ only in respect to where 

 they cut through the meander. These cross sections should be viewed in 

 conjunction with figures 8, 9, and 10, the surface and 200- and 450- 

 meter analyses, respectively. The cold Slope Water, originally observed 

 only north of 38°N, has now pushed southward across 38°N at all depths. 

 Its southward advance appears in the cross section at 37°30'N as it 

 intrudes beneath the warmer water. Farther south (figures 18 and 19, 

 phase II), a deep warm cell (F) is associated with an isothermal layer 

 of 120 meters. The structure of this cell is similar to that observed 

 on the edge of the area during phase I between 36°N and 36°30'N at 65°W 

 and may be the same cell. Cold water directly beneath the warm cell at 

 37°N could be either the advancing Gulf Stream meander or the remnants of 

 the cold ring (C) . The southernmost cross section along 36°N (figure 20, 

 phase II) is typical of the Sargasso region. 



3. Special Gulf Stream Cross Sections 



During phase I, a special crossing of the Gulf Stream was made from 

 39°20»N to 38°34'N and back to 39°N along 65°W (figure 21). BT's were 

 taken at 1-km intervals, and the positions are plotted on the figure. 

 The cross sections, by virtue of covering a short horizontal distance, 

 show the complex structure of the wall. The cross sections are similar 



