130 



WIND CURRENTS AND WIND WAVES 



maintenance of ocean currents. Boundary conditions and converging 

 or diverging wind systems in certain regions must lead to an accumulation 

 of light surface waters, and in other regions to a rise of denser water from 

 subsurface depths. Thus the wind currents lead to an altered distribu- 

 tion of mass, and consequently to an altered distribution of pressure that 

 can exist only in the presence of relative currents. These processes will 

 be illustrated by a few examples. 



INITIAL 



STAGES 



PLAN 



STATIONARY 



PLAN 



CONDITIONS 



PROFILE 



Fig. 33. Schematic representation of effect of wind toward producing currents 

 parallel to a coast in the Northern Hemisphere and vertical circulation. \V shows 

 wind direction and T shows direction of transport. Contours of sea surface shown by 

 lines marked Z), £) + 1. . . . Top figures show sinking near the coast, bottom figures 

 show upwelling. 



Consider in the Northern Hemisphere a coast line along which a wind 

 blows in such a manner that the coast is on the right-hand side of an 

 observer who looks in the direction of the wind (fig. 33). At some dis- 

 tance from the coast the surface water will be transported to the right 

 of the wind, but at the coast all motion must be parallel to the coast line. 

 Consequently, the convergence that must be present off the coast leads to 

 an accumulation of light water along the coast. This accumulation 

 creates an internal field of pressure with which must be associated a current 

 running parallel to the coast in the direction of the wind. Thus, the wind 

 produces not only a pure wind current but also a "relative" current that 



