CONTENTS 



Page 



Introduction 1 



Topography and climatology of the Tehuantepec region 2 



Previous oceanographic information; 



Mean surface temperature 4 



Mean surface current 5 



Mean depth of mixed layer 5 



Mean standing crop of zooplankton 5 



Data from Expedition EASTROPIC 5 



Observations on cruise TO-58-1, Expedition SCOT (May and June 1958) 6 



Horizontal distributions of properties 6 



Vertical distributions of properties 8 



Interpretation 9 



Observations on cruise TO-58-2 (November 1958) 9 



Horizontal distributions of properties , 9 



Vertical distributions of properties 11 



Interpretation 13 



Observations on cruise TO-59-1 (January and February 1959) 15 



Horizontal distributions of properties 15 



Vertical distributions of properties 17 



Interpretation 18 



Observations on cruise TO-59-2 (September 1959) 21 



Horizontal distributions of properties 22 



Vertical distributions of properties 23 



Interpretation 23 



Discussion 24 



Summary 27 



Literature cited 28 



FIGURES 



1. General topography of the Isthmus of Tehuantepec 3 



2. Average surface wind and current in the Gulf of Tehuantepec: current diagrams 



schematic; broken and unbroken arrows indicate, respectively, currents less than 



and more than 10 miles per day 4 



3. Track chart of cruise TO-58-1, Expedition SCOT, in the Gulf of Tehuantepec 6 



4. Horizontal distributions of properties on cruise TO-58-1 7 



5. Surface chlorophyll a and in situ productivity measurements from all cruises in the 



Gulf of Tehuantepec 8 



6. Vertical distributions of properties on cruise TO-58-1 along section A-A (see fig. 3); 



depth scale in m. T, temperature; S, salinity; 67', thermosteric anomaly; O2, oxygen; 



PO^-P, phosphate-phosphorus 10 



7. Vertical distributions of properties on cruise TO-58-1 along section B-B (see fig. 3); 



depth scale in m. T, temperature; S, salinity; 6 j, thermosteric anomaly; O2, oxygen; 



PO4-P, phosphate- phosphorus 11 



8. Track charts of cruise TO-58-2, parts 2 and 3, in the Gulf of Tehuantepec 12 



9. Surface current (GEK) and temperature distributions on cruise TO-58-2, part 2 13 



10. Horizontal distributions of properties on cruise TO-58-2, part 3 14 



11. Vertical distributions of properties on cruise TO-58-2, parts 2 and 3, along section A-A 



(see fig. 8); depth scale in m. T, temperature; S, salinity; 6 j, thermosteric anomaly; 



O2, oxygen; PO4-P, phosphate-phosphorus 16 



12. Vertical distributions of properties on cruise TO-58-2, parts 1, 2, and 3, along section 



B-B (see fig. 8); depth scale in m, T, temperature; S, salinity; 6 j, thermosteric 



anomaly; O2, oxygen; PO4-P, phosphate-phosphorus 17 



lU 



