458 Water Bodies and Stationary Current Conditions at Boundary Surfaces 



between the Greenland Current water and the almost homogeneous Atlantic Water 

 (a = 28-1). The wedge-shaped spreading of lighter polar water over the heavier 

 Atlantic Water to the east stands clearly out. Taking a^ — 21 -X for the polar water 

 and a velocity i\ of about —25 cm/sec (towards the south) and a^ = 28-1, 

 Ta = —5 cm/sec (towards the south) for the Atlantic Water, then equations (XIV.6 

 and 7) give the boundary surface slope as y = 0° 10' 2" which corresponds to 1 :343 

 rising towards the east and for the slope of the physical sea level and that of the 

 isobaric surfaces in the Greenland Current one obtains ^S^ = 0° 0' 0-7" which is about 

 35 cm in 100 km towards the west. The slope calculated for the boundary surface is in 

 good agreement with that actually found. The rise of the physical sea level towards 

 the coast is rather remarkable and even these simplified assumptions lead to the con- 

 clusion that the sea level along the east coast of Greenland will be on the average about 

 20-30 cm higher than in the central parts of the Norwegian Sea. 



3. Stable Stratification of Water Masses 



Water bodies are frequently found in the ocean, situated in a remarkable way side 

 by side, which are apparently in stable equilibrium. This can only occur if certain 

 definite current conditions are present in each water mass. The resulting upwelling 

 and sinking water movements in these water masses must be counter balanced by the 

 current system present. These conditions take a simple form, if one considers at first 

 water bodies arranged in strips which are motionless and are embedded in moving 

 adjacent water masses of a different type (Defant, 1929 b). 



(a) A Motionless Heavy Water Body Embedded into Moving Light Water Masses 



The conditions required for stationary equilibrium are shown schematically in 

 Fig. 201 (Northern Hemisphere; reversed current directions in the Southern Hemi- 

 sphere). This is readily understood on the basis of the rule given above. In the heavier 



Heavier water 



Fig. 201. Motionless heavy water mass embedded in moving lighter water (Northern 



Hemisphere). 



water body the pressure at the same level must be lower than in the surrounding water 

 and correspondingly the physical sea level will be lower than on either side. An 

 elongated depression of it will thus indicate on the sea surface the position of the 

 heavier water body which extends in wedge-form in the deeper layers underneath the 

 moving water masses to either side. If the water body in the middle between the moving 

 water masses is not motionless then this movement must be added vectorially to the 

 currents of the surrounding water masses on both sides in order to conserve a stable 



