460 



Water Bodies and Stationary Current Conditions at Boundary Surfaces 



206 205 204 203 202 201 



60 "^ 



" 40 



I 20 



c 



Q 0- 



Sea surface 



50 dbar (m) 



250 dbar (m) 

 450 dbar (m) 



750dbar 



Fig. 203. Distribution of the specific volume anomaly. Form of the physical sea surface and 

 of the isobaric surfaces in a meridional cross-section south of the Great Banks of New- 

 foundland. 



in the deeper layers due to the wedge-shaped spreading of the adjacent heavier waters 

 underneath, which in the absence of the effect of Earth rotation would press upwards 

 the lighter water in the middle. The equilibrium of all the forces prevents this upward 

 movement and maintains the structure in a stationary state. 



This simplest arrangement of water bodies is not readily found in ocean currents. 

 Dietrich (1935) in an investigation of the Agulhas Current found a mass distribution 

 which was similar to that pictured in Fig. 204, although with the current directions 

 exactly opposite that in Fig. 204. The pressure distribution as well as the topography 

 of the physical sea level would then be different. Dietrich assumed rising isobaric 

 surfaces towards the central lighter water body and no motion in the lighter body 

 (planar sea level and isobaric surfaces). The gradient currents in the adjacent heavier 

 water masses then correspond to the pressure field, but the current system as a whole 

 does not correspond to the rule of a stable position of the boundary surface. The 

 schematic representation given by Dietrich is in error. 



^°^y ^^r 



Fig. 204. Motionless lighter water mass embedded in moving hcaNier water (Northern 



Hemisphere). 



