because of the transition period in January February, when 

 one group of cadeta goes back to school and a new group 

 begins sea duty. 



TRANSECT ANALYSIS 



Gulf of Mexico 



Over the years there have been several descriptions of 

 the Yucatan Loop /Florida Current regimes, but many 

 ambiguities still exist. For purposes of this report, I have 

 used the criteria of Nowlin and McLellan (1967) for 

 describing the Loop Current as that water within the Gulf of 

 Mexico that has just passed through the Yucatan Channel 

 ;ind has not yet exited through the Straits of Florida (usually 

 about midway between Cuba and the western Florida Keys). 

 The current flow into the Gulf of Mexico between the 

 h estcrn tip of Cuba and the Yucatan Peninsula was referred 

 to as the Yucatan Current and the current flow upstream 

 from there (into the Caribbean Sea) was referred to as the 

 Caribbean Current. 



Loop Current.— The Loop Current showed up on 

 transects conducted in January, February, April, August, 

 October, and November (Figs. 1-6). The downward slope 

 (southward) of the isotherms, such as between stations 16 

 and 17 in Figure 1 for January, indicated the approximate 

 position of the Loop Current as it passed from the Yucatan 

 Channel into the Gulf of Mexico. About a month later the 

 Loop Current was transected again near the Yucatan 

 Channel as shown by the slope of the isotherms between 

 stations 7 and 8 in Figure 2. 



In April (Fig. 3), the Loop Current was found between 

 stations 5 and 6. A comparison of Figures 1, 2, and 3 shows 

 the Loop Current extending further into the Gulf of Mexico, 

 from its January position at approximately lat. 23°N to 

 approximately lat. 24°N in February and to lat. 25°N in 

 April. This northward migration was consistent with 

 previous observations of the behavior of this current 

 (Boisvert 1967). 



The complex temperature structure of the section made 

 in August (Fig. 4) requires a close examination of the data to 

 discern the difference between Yucatan Current, Loop 

 Current, and an associated eddy. At this time, I feel the 

 Yucatan/Loop Current system was transected four times. 



Following the temperature structure from south to 

 north, the downward tilting of the isotherms between 

 stations 29 and 28 indicated the normal westward flow of the 

 Caribbean Current just prior to entering the Yucatan 

 Channel. The upward tilting of the isotherms between 

 stations 26 and 23 indicated an eastward flow (into the page 

 in the vertical section), and the downward tilt of the 

 isotherms between stations 20 and 19 indicated a westward 

 flow. Finally, the structure between stations 16 and 12 

 indicated eastward flow, apparently the northernmost 

 crossing of the Loop Current. The configuration of the 

 isotherms between stations 10 and 1 suggest the presence of 

 a warm core eddy and are discussed in the following section. 



Another possibility was that the flow pattern through 

 the Yucatan Channel had diverged and become multiaxial as 

 suggested by Cochrane 2 in 1963, with more eastward 



'Cochrane, J. D. 1963. Yucatan Current. Texas A&M College, 

 Department of Oceanography and Meteorology, Ref. 63-18A. Unpubl. 

 rep., 25 p. Atlantic Environmental Group, National Marine Fisheries 

 Service. NOAA, Narragansett, RI 02882. 



divergence flowing around Cuba and into the Straits of 

 Florida; and the western axis looping through the Gulf 

 between stations 16 and 12 at about lat. 25°N. 



In later crossings the Loop Current appeared to recede 

 from the Gulf. In October it was crossed at about lat. 24°N 

 (Fig. 5, stations 16-21) and in November at about lat. 22°N 

 (Fig. 6, stations 14-16). 



Eddies. — Eddy structures were detected in the north- 

 eastern Gulf of Mexico on transects conducted in January, 

 February, August, and October (Figs. 1, 2, 4, 5). In January 

 (Fig. 1) the temperature structure between stations 17 and 

 21 showed some evidence of a weak anticyclonic eddy with a 

 diameter of approximately 125 nautical miles. 



In February (Fig. 2), the doming effect of the isotherms 

 between stations 1 and 7 suggested the existence of a warm 

 core anticyclonic eddy, possibly a recrossing of the same 

 eddy seen the previous month. Unfortunately, the lack of 

 XBT observations to the north of station 1 prevent the 

 positive identification of this structure as a remnant 

 anticyclonic eddy. 



In August (Fig. 4), the temperature structure found 

 between stations 10 and 1 was an indication of a warm core, 

 anticyclonic eddy that has possibly broken off from the main 

 flow of the Loop Current. This was consistent with past 

 observations of Loop Current activity (Leipper 1970). The 

 width of the eddy at this crossing was about 125 nautical 

 miles and extended to depths of greater than 700 m. 



In October (Fig. 5), another warm core, anticyclonic 

 eddy was transected. The transect crossed through the eddy 

 between stations 5 and 11 (approximately 125 nautical miles) 

 and the eddy extended to a depth of greater than 750 m. 



Caribbean Current.— The Caribbean Current, described 

 by Boisvert (1967) as one of the most persistent and well 

 defined of the major currents, is broad and relatively slow 

 moving. It was seen in the SOOP transects south of the 

 Yucatan Channel as a northward declination of isotherms. 

 Utilizing this characteristic, we found the Caribbean 

 Current in February, April, August, and November (Figs. 

 2, 3, 4, 6). 



In February (Fig. 2), the Caribbean Current was crossed 

 between stations 13 and 22. Temperature structure between 

 stations 19 and 21 indicated an area of possible counterflow. 



In April (Fig. 3), the Caribbean Current was again 

 indicated by the general upward incline of the isotherms 

 between stations 9 and 15. 



In August (Fig. 4), the upward incline of the isotherms 

 between stations 28 and 29 indicated the westward flow of 

 the Caribbean Current just prior to entering the Yucatan 

 Channel. 



In November (Fig. 6), an indication of the Caribbean 

 Current appears between stations 16 and 20. 



Western North Atlantic 



Features described in the western North Atlantic include 

 the North Wall of the Gulf Stream, Shelf Water-Slope Water 

 front, bottom cold cell, and eddies formed by the Gulf 

 .Stream. Temperature sections obtained on four New York 

 to Bermuda sections made during May, June, and November 

 (Figs. 7-10) show some of these features. 



Gulf Stream. -Using the criterion of 15°C at 200-m depth 

 (Worthington 1964) to indicate the North Wall of the Gulf 



