\Z0' 



30° M 1 1 1 1 1 1 1 1 1 1 1 1 M M 



FISHERY BULLETIN: VOL. 72. NO. 4 

 80° 70° 



I I I I I I I I U 30' 



20' 



10° 



10° 



-I I I I I I ' I I I I 1 I i I I I I I I  I I I I I I I I I i I I I I I i I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I 1 I I I  1 I I I I I I  I  I I I . I I i  I I I i I i 



130° 



120° 



110° 



100° 



90° 



80° 



70° 



Figure 3. — Geopotential anomaly, in joules per kilogram (dynamic decimeters), at the sea surface relative to 500 db in June-July 

 1967. EASTROPAC cruise ZJacfc/ Starr Jordan 30. The position of the intertropical convergence zone at the eastern and western ends 

 of the map is indicated by triangles. 



9°N, long. 89°W (Brandhorst, 1958; Cromwell, 

 1958; Wooster and Cromwell, 1958; Wyrtki, 

 1964) in February-March 1967 and February- 

 April 1968 (Figures 1 and 7), but is less well 

 defined in August-September 1967 (Figure 4). 



Between Costa Rica and Cape Corrientes (lat. 

 20°N), nearshore flow is generally northwestward 

 in August-September (Figure 4), when the North 

 Equatorial Countercurrent is strongly developed. 

 In the other months (Figures 1-3 and 5-7) flow is 

 southeastward from Cape Corrientes at least as 

 far south as the Gulf of Tehuantepec (lat. 16°N). 

 This sense of flow is in agreement with that found 

 on the H. O. 570 drift charts except for June- July, 

 when the nearshore current is northwestward on 

 the drift charts. Puis' (1895) charts, however, in- 

 dicate easterly components of flow near the coast 

 between Cape Corrientes and the Gulf of Tehuan- 

 tepec in all months of the year. 



North Equatorial Countercurrent 



Previous studies (e.g., Wyrtki, 1965) have indi- 

 cated that the North Equatorial Countercurrent 

 is subject to a large variation in response to that 

 of the atmospheric circulation, particularly the 

 annual meridional migration of the intertropical 

 convergence zone (ITCZ). During EASTROPAC 

 the North Equatorial Countercurrent exhibited a 

 high level of variability in position and intensity. 

 The Countercurrent was weak and discontinuous 

 in February-April 1967 and 1968, when the ITCZ 

 lay near its southernmost position at lat. 2°-6°N. 

 It was strong, broad, and extended all the way to 

 the coast of Costa Rica in August-September 

 1967, when the ITCZ lay near its northernmost 

 position at lat. 11°-15°N. (The position of the 

 ITCZ during EASTROPAC can be inferred from 

 surface-wind charts in the EASTROPAC atlas. 



1080 



