102 



Linear Theories — Viscous 



Pacific Ocean more properly than the rectangular model. Munk, Groves, 

 and Carrier (1950) have studied the effect of the nonlinear inertial terms, 

 assuming they are small, using a method of successive approximations, and 

 using Reid's (19486) model of vertical density structure, which consists of 

 an exponential decrease of density upward to the thermocline, and a 

 homogeneous upper layer. They found a sHght do^vnstream displacement 

 of the region of maximum currents. The two important observed features 



400 KM 



Fig. 63. The volume -transport stream function, in units of 10* m.'/sec, near 

 the western boundary for mean annual zonal winds over the Atlantic. The 

 center line is at 31° N. For comparison with the Sargasso Sea circulation, the 

 figure should be distorted by maintaining the west-east orientation of the 

 a;-axis and rotating the 2/-axis clockwise until it coincides with the coast. From 

 Mimk (1950, fig. 5). 



which were not accounted for in the linear theory, (i) the inshore counter- 

 current and (ii) the continued sharpness of the Gulf Stream long after it 

 leaves the coast, were not found in the higher-order solutions. Sub- 

 sequently, Miyazaki (1952) found that an inshore countercurrent (i) can 

 be obtained formally by letting the coefficient of eddy viscosity decrease 

 toward the coast, and, as we shall see in the next chapter, there is no 

 difficulty in obtaining feature ii if the inertial terms are large enough. 



So much of the quantitative aspects of the theory of wind-driven ocean 

 currents depends upon the actual pattern of wind stress used that it is 

 advisable to reproduce for reference the actual distribution of zonal mnd 

 stress which Munk has adopted (fig. 64). 



