264 



WOOSTER AND RE IP 



[CHAP. 11 



minimum which lies at intermediate depths. In the eastern boundary currents, 

 isopleths of dissolved oxygen ascend toward the coast, where the oxygen 

 minimum is shoalest and has the lowest oxygen content. Thus, in sub-surface 

 charts of the horizontal distribution of dissolved oxygen, wedges of low oxygen 

 extend westward from the regions of eastern boundary currents (e.g. Watten- 

 berg, 1938. fig. 5). This condition appears to be more strongly developed over a 

 larger area in the Pacific than in the Atlantic Ocean, although the extensive 



(a) (b) 



(c) (d) 



1000 



DISTANCE OFFSHORE (km 



Fig. 9. Profiles across Benguela Current at 24°S, October, 1958. (a)-(d) as in Fig. <>. 

 (After Fuglister, 1960.) 



development of the anaerobic and "azoic" conditions on the sea floor near 

 Walvis Bay (Hart and Currie, 1960) is apparently not equalled in the Pacific. 

 At times coastal upwelling is so intense that nearshore surface waters are 

 significantly undersaturated. Thus, surface saturation values as low as 36° 

 and 50% have been reported off the Peruvian coast (Posner, 1957; Discovery 

 Committee, 1949), 70% off the Canary coast (Fuglister, 1960) and even 6% off 

 Walvis Bay on the southwest coast of Africa (Hart and Currie. 1960). Such low 

 oxygen values do not occur off the California coast. 



