464 Water Bodies and Stationary Current Conditions at Boundary Surfaces 



(disregarding friction). The current system can only be stabilized by distributions 

 pictured in cases c and d. In both cases a counter current flowing eastward must be 

 introduced between the westward flowing equatorial currents of the Northern and 

 Southern Hemisphere. In case c it lies entirely within the Northern Hemisphere, 

 together with parts of the South Equatorial Current which extends across the equator; 

 in case d the counter current is broader and extends somewhat across the equator into 

 the Southern Hemisphere. This kind of adjustment position of the pressure surfaces 

 and of the boundary surface, thus satisfies the requirements of a boundary surface 

 slope for moving water bodies. 



These theoretical considerations can be tested by using the available observational 

 data. Figure 209 presents for a meridional profile, along the strongest inclination of the 

 surfaces, the topography of the pressure surfaces and of the physical sea level of the 



*20 

 dyncm 



♦ 70 - 



— 



-10 - 



-20 — 



Z(f S 10° 



(f 



10° N 20° 





/ 



K/ 



/X 



/ 



./• 



V-7- 



-^130 

 160 



■i200 



J i 



\i 



Fig. 209. Meridional cross-section through the Atlantic Ocean (25° N. to 25° S., 20° W. to 



30° W.). Upper picture: physical sea surface (relative to the lower current 400:1 exaggerated). 



Lower picture: depth of the thermocline (tropospheric discontinuity layer). 



Atlantic Ocean. The structure shown corresponds entirely to that given in Fig. 207c. 

 There is no doubt that the adjustment of the tropospheric discontinuity layer is 

 dynamically controlled and to a large extent imposed by the arrangement of the ocean 

 currents in the top layer ; there seems to exist a very close mutual adjustment between 

 them. The observed slope agrees not only quantitatively but also qualitatively with 

 that required by theory (Table 132). If the slope of the boundary surface, given in 

 metres per 3 degrees of latitude, is denoted by / and that of the physical sea level 

 by /i, then taking a mean value for pi of 1-024 and putting /= / x 10^^ the formula 

 (XIV.8) gives 



/ 



3-46 



and 



/. = 



-9-77 X 10-* m. 



The value for r^ is taken as the approximate average over the entire top layer. The 

 observed and calculated values are nearly equal. 



