Further details concerning the acquisition or process- 

 ing of data from the cruises considered here can be ob- 

 tained from the authors. 



For purposes of this report all descriptive figures have 

 been included within the text and all vertical tem- 

 perature sections have been organized geographically 

 and chronologically and included as Appendix Figures. 



TRANSECT ANALYSIS 



Gulf of Mexico 



(Fig. 1, Appendix Figs. 1-16) 



Loop Current. — In 1974 the Loop Current was crossed 

 on seven occasions (Table 1) by SOOP ships. There were 

 two crossings in March (Appendix Figs. 1, 2), one in 

 April (Appendix Fig. 3), two in May (Appendix Figs. 4, 

 5), and one each in June (Appendix Fig. 6) and July (Ap- 

 pendix Fig. 8). 



Utilizing 20°C at 125 m as the left edge of the Loop 

 Current (G. A. Maul, pers. commun.), the position of the 

 front can be monitored from XBT data. Most mi- 

 grations of the Loop Current edge ranged between lat. 

 22°N and 24°N. Movements of more than 1° of latitude 

 in less than 2 wk were not uncommon. One migration of 

 about 90 nautical miles (167 km) occurred within 9 days, 



1 1 



.1 7 



T -"'" — "'/ 



'""^ S*^ MAT 21,1974 / 



JULY 20-21.1974 // 1 







^S . /-JULY 6-7,197-i 





:X5 ^^ 





V i 



Figure 1. — Composite plot of Gulf of Mexico eddy positions. 



between 28 June (Appendix Fig. 6) and 7 July (Appen- 

 dix Fig. 8). 



The Loop Current was crossed by the Delta Sud on 9 

 March at lat. 23°15'N at station 23 (Appendix Fig. 1). 

 Again on 23 March at lat. 22°30'N the Delta Norte cross- 

 ed the Loop Current between stations 12 and 13 (Appen- 

 dix Fig. 2). 



In April (Appendix Fig. 3) a crossing of the Loop Cur- 

 rent by the Delta Sud determined the front to be at lat. 

 22°N. 



In May (Appendix Fig. 4) the Loop Current appeared 

 as a broad flowing current between stations 40 and 32. At 

 this time the front's position had intruded up to lat. 

 24°N. Again in May (Appendix Fig. 5), the Delta Sud 

 crossed the Loop Current between stations 22 and 24. At 

 that time the front had receded back to lat. 23°N. 



In June (Appendix Fig. 6) the Loop Current again ap- 

 peared as a broad flow between stations 9 and 2. The 

 main front (20°C and 125 m) showed up between stations 

 7 and 8 at about lat. 24°N. Also present at this time was 

 a counterflow around Cuba that showed up between 

 stations 1 and 2. 



In July (Appendix Fig. 8), the Loop Current was cross- 

 ed at lat. 22=30^ between stations 17 and 18. 



Eddies.— In 1974 the SOOP ships in the Gulf of Mex- 

 ico crossed eddies most of which were anticyclonic with 

 warm-cores on 19 occasions (Table 2). Eddies were cross- 

 ed in March through August and November (Appendix 

 Figs. 1-7, 9-14). The diameters of these eddies where 

 crossed ranged from about 75 nautical miles (138 km) to 

 335 nautical miles (621 km) and ranged in depth from 

 200 to 700 m. Some eddies were crossed more than once. 

 One anticyclonic eddy (Appendix Figs. 4, 7, 9) in par- 

 ticular was easy to track because it had a subsurface sig- 

 nature in the form of a peak in the 26° isotherm that was 

 opposite to the rest of the isotherms. This peak also hap- 

 pened to occur at the center of the eddy. This eddy was 

 crossed on 21 May (Appendix Fig. 4), 7 July (Appendix 

 Fig. 7), and 21 July (Appendix Fig. 9) and migrated in 

 position from lat. 26°24'N, long. 87°52'W (Appendix Fig. 

 4) to lat. 24°55'N, long. 88°55'W (Appendix Fig. 7) to 

 lat. 25°26'N, long. 89°44'W (Appendix Fig. 9). On all 

 crossings the eddy structure extended to depths of 

 greater than 600 m. The eddy moved 140 nautical miles 

 (259 km) in 2 mo in a southwesterly direction or about 2.3 

 nautical miles (4.3 km)/day (Fig. 1). 



Table 1. — Crossings of the Loop Current made by SOOP vessels in 

 1974. 



Appendix 





Station 





figure 



Ship 



no. 



Date 



1 



Delta Sud 



20-23 



8-9 Mar. 



2 



Delta Norte 



11-15 



21-23 Mar. 



3 



Delta Sud 



28-31 



15-17 Apr. 



4 



Delta Sud 



40-32 



21 May 



5 



Delta Sud 



22-24 



27-29 May 



6 



Delta Sud 



9-2 



28-29 June 



8 



Delta Sud 



17-20 



7-8 July 



Low salinity surface water. — River runoff along the 

 Gulf coast, which forms a plume detectable by low sur- 

 face salinities (<34.5°/ 00 ), sometimes extended great 

 distances offshore (well beyond the shelf break). Nine 

 transects of low salinity water were detected in 1974 

 (Table 3). Crossings in March, April, May, June, July, 

 and August (Appendix Figs. 1, 3, 4, 6, 7, 9-12) showed 

 large variations in salinity ranges and horizontal extent. 



At times the extent of the low salinity surface waters in 

 the eastern Gulf of Mexico seemed to be controlled by the 

 northward migrations of either eddies or the Loop Cur- 



