Oceanic Conditions off Northeastern Brazil 

 February -March and October -November 1966 



Merton C. Ingham^ 



and 



Robert B. Elder' 



INTRODUCTION 



An investigation of the interchange between 

 the North and South Atlantic oceans was begun 

 by the U.S. Coast Guard Oceanographic Unit 

 (CGOU) in 1966. The press of other duties has 

 prevented the completion of this investigation, 

 but a series of oceanographic sections was com- 

 pleted in the western tropical Atlantic off 

 Fortaleza, Brazil (fig. 1). These sections were 

 intended to transect the Guiana Current, the 

 northern branch of the South Equatorial Cur- 

 rent, and the Equatorial Undercurrent. 



Since 1966, the work of several oceanogra- 

 phers (Cochrane, 1968; Metcalf and Stalcup, 

 1967; and Metcalf, 1968) has shown the pat- 

 tern of surface and near-surface currents in 

 the western equatorial Atlantic to be more 

 complex than formerly realized. Because of the 

 incomplete state of understanding of this area 

 at the time, planning of the sections occupied 

 by USCGC EVERGREEN, USCGC EAST- 

 WIND, and USCGC ROCKAWAY did not yield 

 optimum placement of the transects for inter- 

 section with the Equatorial Undercurrent or 

 the currents flowing into it; however, four 

 shallow currents, including the Equatorial Un- 

 dercurrent, were intersected by one or more of 

 the transects. 



DATA ACQUISITION AND PROCESSING 



Temperature data were acquired with paired 

 reversing thermometers on Nansen bottles, and 

 mechanical or electronic bathythermographs. 

 The acquisition and processing of temperature 

 data generally followed the procedures specified 

 by the U.S. Naval Hydrographic Ofiice Publi- 



1. U.S. Coast Guard Oceanographic Unit, Washington, 

 D.C. 20390. 



cation No. 607 (1955) and LaFond (1951), and 

 a PDP-5 digital computer was used for ther- 

 mometer corrections. 



Salinity samples were collected with teflon- 

 lined Nansen bottles and analyzed on board with 

 inductive salinometers. The salinometers were 

 calibrated with standard (Copenhagen) water 

 at least once per 30 samples. 



Sampling depths were determined with paired 

 protected and unprotected reversing ther- 

 mometers or interpolated from L-Z curves based 

 on thermometer performance and wire angle. 

 Procedures used for these determinations were 

 essentially those specified by LaFond (1951). 



The concentration of dissolved oxygen was 

 determined for water samples drawn from Nan- 

 sen bottles on board ROCKAWAY and EAST- 

 WIND. A modified Winkler titration (Strick- 

 land and Parsons, 1965) was used for this 

 determination. 



All oceanographio and meteorological data 

 acquired on station were quality-controlled at 

 CGOU, then submitted to the National Ocean- 

 ographic Data Center (NODC) for further 

 processing and listing (reprinted in Appendix 

 I). The NODC output, in punched card format, 

 was used to construct vertical sections of tem- 

 perature, salinity, sigma-t, and oxygen with a 

 computer-driven automatic plotter using a com- 

 puter program developed by Richard F. John- 

 son (description in preparation). The result- 

 ing sections were quality-controlled and 

 smoothed by hand to yield plates of publication 

 quality. The final form of the temperature, 

 salinity, and density sections are included in 

 this report (figs. 2-22). 



Further details concerning the acquisition or 

 processing of data from the cruises considered 

 here can be obtained from CGOU. 



