masked by the relatively slow boundary processes of radiation and sea-air 

 interchange. 



The two vertical temperature sections, Figures 16 and 17, clearly show 

 the water mass of the Equatorial Countercurrent (hereafter ECC) occupy- 

 ing the surface layer. This surface layer presumably rests on the subtropical 

 component of the Peru Current, which according to Gunther (1936:160) 

 flows north beyond Pt. Santa Elena and, as will be seen in a later section, 

 probably at least as far north as the Isla La Plata. As the ECC crosses 

 the geographic equator and flows toward the south it will, on the basis of 

 conservation of angular momentum, acquire anticyclonic vorticity and tend 

 to hug the South American shores. This would tend to lead to a greater 

 thickness of the ECC nearer shore. But the observed thickness of this water 

 mass, as defined by the depth of the thermocline, is clearly shown in Fig- 

 ure 17 to be smaller near shore than off"shore. Since the observed winds 

 made at the time of BT lowerings as well as the climatological winds as 

 given by charts published by Compania Administradora del Guano (Lima, 

 Peru) are stronger offshore than near shore, it is possible that the greater 

 thickness offshore may be due to stronger wind mixing. However, although 

 there are no salinity data to corroborate this and the situation is further 

 complicated by upwelling, the greater warming of the subtropical water 

 beneath the ECC at stations 1 7 and 1 8 implies that differential wind mix- 



70.9 



ire Dldnco 



Figure 15. Surface Temperature in degrees Fahrenheit. August. l'-^54. 

 58 • 



