INTERPRETATION OF RESULTS 



Four shallow currents and two intermediate 

 depth water masses were portrayed in the 

 USCGC EVERGREEN, USCGC EASTWIND, 

 and USCGC ROCKAWAY sections (figs. 2-22) . 



North Brazilian Coastal Current 



Investigations by Cochrane (1968) and Met- 

 calf and Stalcup (1967) have revealed a strong 

 (up to 2.8 kts.) northwestward current extend- 

 ing from Cape Sao Rogue, Brazil (about 5°S) to 

 about 4-6°N. This current, called the North 

 Brazilian Coastal Current by Metcalf and Stal- 

 cup, is believed to be discontinuous with the 

 Guiana Current, which also flows northwest- 

 ward, roughly parallel to the coastline, from 

 about 4-6°N to the vicinity of Trinidad (about 

 11°N), where it enters the Caribbean Sea. The 

 North Brazilian Coastal Current was shown by 

 these investigators to include a tongue of rela- 

 tively high salinity (near 37.0°/oo), whose core, 

 a layer of maximum salinity, is located at about 

 80 to 100 meters. The current, carrying the sub- 

 surface layer of high salinity, was portrayed as 

 turning anticyclonically just north of the 

 equator and entering the Equatorial Under- 

 current, providing that current with its charac- 

 teristic high salinity. Goulet and Ingham (in 

 preparation) have shown that the source of 

 the high salinity core of the North Brazilian 

 Coastal Current is an area of high salinity at 

 the sea surface near the South American conti- 

 nental margin at about 18-22°S. 



Evidence for the presence of the North Bra- 

 zilian Coastal Current was found in the distri- 

 butions of salinity and density observed on the 

 EVERGREEN, EASTWIND, and ROCKAWAY 

 cruises. During each cruise a cell of relatively 

 higher salinity (36.5-36.8°/oo) was found at 

 the shoreward end of each transect in the layer 

 of hi^ salinity (figs. 2, 5, 8, 11, 14, 17 and 20) 

 at about 80 to 100 meters. The density structure 

 of the layer of high salinity in the vicinity of 

 the cells (figs. 4, 7, 10, 13, 16, 19 and 22) gener- 

 ally involved an inclination of the cti isopleths 

 (downward from offshore to onshore) which 

 implied a northwestward geostrophic current. 

 Whenever the layer of high salinity contained 

 two cells of relatively higher salinity south of 

 the equator, such as on the two southernmost 

 ROCKAWAY sections (figs. 14 and 17), the 

 corresponding density structure (figs. 16 and 



19) indicated northwestward flow in the cells 

 and a southeastward countercurrent between 

 them. 



Equatorial Undercurrent 



The structure and extent of the Atlantic Equa- 

 torial Undercurrent have been investigated by 

 many oceanographers, but only recently has the 

 Undercurrent been described off northeastern 

 Brazil in the area of its origin (Cochrane, 1963, 

 1965 and 1968 ; Metcalf and Stalcup, 1967) . The 

 Undercurrent, identified in vertical salinity sec- 

 tions by a subsurface cell of relatively high 

 salinity (>36.2°/oo) on or near the equator at 

 about 70 to 100 meters, was found to be defi- 

 nitely present during three of the Coast Guard 

 transects (figs. 2, 5 and 14) . Its absence during 

 the third EVERGREEN transect (fig. 8) , which 

 was conducted along the same track as the sec- 

 ond but five days later, gives some indication 

 of the variability of the Equatorial Undercur- 

 rent in this area. Either the Undercurrent occa- 

 sionally loses its characteristic high salinity or 

 its flow at that longitude (33°W) is not steady, 

 perhaps because the current's initial point of 

 contact with the equator shifts. The cell of high 

 salinity was present during the first (southern- 

 most and easternmost) transect of the ROCK- 

 AWAY series (fig. 14), but was absent from 

 the second and third transects (figs. 17 and 20). 

 The point of intersection of the first ROCK- 

 AWAY transect with the equator (29°W) was 

 about 240 nautical miles east of the point of 

 intersection of the EVERGREEN transects, 

 which supports the contention that the Under- 

 current's initial contact with the equator shifts. 



Only slight inclinations of isopycnal (iso-o-t) 

 surfaces were observed in and near the cell of 

 relatively high salinity associated with the 

 Equatorial Undercurrent, but this is to be ex- 

 pected because of the inverse relationship 

 between the inclination of the field of mass and 

 the sine of latitude in the geostrophic equation. 

 Spreading of the pycnocline on or near the equa- 

 tor, another characteristic associated with the 

 Undercurrent, was pronounced only in the first 

 ROCKAWAY transect (fig. 16) . 



South Equatorial Current 



Westward flow in the surface layer in the 

 equatorial Atlantic Ocean constitutes part of a 

 current system called the South Equatorial Cur- 



