PREVAILING 

 WINDS 





EKMAN DRIFT 



SURFACE JET 



COUNTER 

 CURRENT 



UNDER CURRENT 



MAIN UPWELLING 



EASTERN BOUNDARY 

 CURRENT 



SECONDARY 

 UPWELLING 



Figure 35. — Schematic view of coastal upwelling. 

 When favorable winds blow towards the Equator, 

 the earth's rotation produces an offshore or 

 Ekman drift of the upper ocean layers along the 

 coast. This drift in turn produces an upwelling of 

 colder, deeper waters near the coast, often a 

 narrow band 10 to 15 kilometers wide. The rich 

 nutrients of the upwelied deeper water cause a 

 rapid growth in the plankton population, which 

 results in a rich feeding ground for fish. This 

 phenomenon is significant because an estimated 

 50 percent of the world's fish supply comes from 

 major upwelling areas. 



37 



