c. 



TEMPERATURE , °C 

 10 15 20 



TEMPERATURE ,°C 

 10 15 20 



25 



30 



100 



e 200 



X 



I- 



Q. 



LJ 



O 300 



400 



500 



100 



E 200 



X 

 h- 

 0. 

 UJ 

 Q 300 





APR/ 

 MAY, 



/f/^<^»auG 







- 





W \JJJN 







APR 



NJUL. AUG 







- 









TAT!CN POSITION 







«o* 





-\ 



f 





JO* 







- 







!0* 



" -"fMawci.on is 







■o- itr -:" 



XT 



15 20 25 30 



500 

 Figure 4. — Continued. 



400 



500 



Coastal Upwelling 



Reid et al. (1958) have described upwelling and the 

 subsurface countercurrent along the California coast 

 from repeated detailed oceanographic observations by 

 the California Cooperative Oceanic Fisheries Investiga- 

 tions (CalCOFI) program. Some effects of upwelling also 

 appear in XBT mean temperatures, although sampling 

 was poor at the California end of the route. In January, 

 Appendix 1, the 9°C isotherm was closest to the surface 

 (about 130 m) some 200 km from the California coast, 

 but bent downward to 150 m at the coast. About late 

 March the 9 C C isotherm began to rise and reached a 

 depth of about 120 m at the coast by mid-June, so that it 

 then had nearly a uniform upward trend approaching the 

 coast. Starting in September it began to sink again at the 

 coast and the "ridge" in the isotherm again moved 

 gradually offshore and by mid-November had returned 

 to the position 200 km offshore where it was in January. 



Coastal upwelling causes a delay in the onset of sum- 

 mer warming and a reduced range of the seasonally vary- 

 ing mean temperature. In the inshore area of the Califor- 

 nia Current (Fig. 3g), after a nearly constant winter 

 temperature of about 12°C, summer warming at the sur- 



face did not begin until late May or early June, as com- 

 pared with April or May farther offshore (Fig. 3e, f). Also, 

 in the inshore area the September temperature max- 

 imum reached only 16°C, for an annual range of only 

 4°C, whereas farther offshore (Fig. 3f) it reached 17.5°C 

 for an annual range exceeding 5°C. 



California Subsurface Countercurrent 



In the vertical sections of Appendix 1 the downwarp- 

 ing of the 6°, 7°, and 8°C isotherms from 200 km at sea to 

 the California coast shows warmer water against the 

 coast (at depths of 200 to 500 m) than offshore. This 

 agrees with observations of Reid et al. (1958) who 

 reported the existence of a narrow northward moving 

 undercurrent against the California coast and below 200 

 m. An exception occurred during April and May when 

 the 8°C isotherm rose to about 200 m at the coast. This 

 indicates that upwelling normally reached to that depth 

 during these months. Another exception was the nearly 

 level approach to the coast of the 8°C isotherm from mid- 

 August to mid-September. This may reflect a brief late- 

 summer upwelling period, but might just be the result of 

 inadequate sampling immediately adjacent to the coast. 



