The cold ring (C) in phase I has apparently disappeared by the 

 time of phase II. The cold water near 37 o N,66°30'W at 450 meters may 

 be a remnant of this ring entrained by the Gulf Stream, or the ring 

 may possibly have moved out of the area entirely. A warm cell (F) at 

 200 meters overrides cold water at 450 meters near 37°N,66°W. 



2. Vertical Cross Sections 



Further insight into the three-dimensional structure and change 

 in the Gulf Stream region can be gained from cross sections drawn for 

 each leg of each GILLISS phase. These cross sections contributed addi- 

 tional knowledge of the thermal structure that was not apparent from the 

 horizontal analyses. 



The northernmost cross section at 40°N (figure 11, phase I) shows 

 more complexity than was apparent in the surface and 200- and 450-meter 

 analyses. A very cold feature (E) appears near 67°W at 50 meters. The 

 cold water is weakly evident at the surface (D) and at 200 m. More sub- 

 surface cold water is present near 69°W. 



The cross section along 39°40*W (figure 12, phase I) reveals the 

 same cold feature (E) near 67°W. The warm eddy (B) which appeared in 

 the horizontal analyses is now evident near 68°W. Farther south, along 

 39°20'W (figure 13, phase I), the cold feature (E) is not apparent at 

 67°W; but the southern portion of the warm eddy is apparent. 



The cross section along 39°N (figure 14, phase I) shows no signifi- 

 cant features, but along 38°30'N (figure 15, phase I) the northern edge 

 of the Gulf Stream appears near 67°W. The Gulf Stream, identifiable as 

 the 24°C water, is located just south of this section from 69°W to nearly 

 67°W, then just north of this section to 65°W (figure 8). The wall of 

 the stream is the sharp gradient zone extending from the surface at 67°W 

 to 120 meters at 65°W. 



The thermal structure of the Gulf Stream is much simpler along 

 38°N (figure 16, phase I). Isotherms become more uniform and inversions 

 are absent, but there is a hint of the Gulf Stream boundary near 69°W, 

 where cold water appears at depth. The temperature of the surface layer 

 in this section is greater than 24°C, indicating that it is the Gulf 

 Stream. The next two sections at 37°30'N (figure 17, phase I) and 37°N 

 (figure 18, phase I) are generally similar to the section along 38°N, 

 but these sections are south of the center of the Gulf Stream, with 

 surface temperatures of 24°C or less. The cold water near 450 meters 

 along 37°N at 67°W is part of the cold ring (C) discussed earlier and is 

 clearly evident at 36°30' (figure 19, phase I). The section along 36°N 

 (figure 20, phase I) is similar to others south of the Gulf Stream. 

 Note that the temperature north of the stream was near 6°C along the 

 bottom of the section (figures 11 through 15, phase I), while bottom 

 temperatures in the stream and south of the stream were greater than 16°C. 



