178 



Salinity of the Ocean, its Variation in Oceanic Space and in Time 



is largely equivalent to the phenomena in a "jet" CFreistrahl) at some distance from 

 the nozzle (Diise). The distribution of^ AjA^ in transverse section is also quite charac- 

 teristic. The maximum appears in the lower part of the spreading layer (150 m be- 

 neath the core) ; below this the ratio falls rapidly, but above only slowly. This striking 

 distribution of the exchange coefficients can be readily explained by the different 

 stability conditions above and below the core. 



+WOm 

 1.2 



o,e 



OA 



0,0 



+200 



-200 



-^00 



Fig. 81. Relative distribution of the exchange coefficients, AlA^ and the current velocity, 

 w/«o along a cross-section through the subantarctic intermediate water along the western 



side of the Atlantic. 



(a) Salinity of the deep water below 1500 m. In the deep layers of the Atlantic the 

 salinity increases slowly from the Antarctic regions across the equator as far as the 

 deep-reach 'ng, warm and high saline water of the northern subtropics (20°-40° N.); 

 from here towards the north it decreases slowly in the upper layers. However, in the 

 deeper layers the increase to about 20°-40° N. is much less. The asymmetry of the 

 salinity distribution shown so strongly in the subantarctic intermediate water is also 

 present in the deeper layers but not to the same extent. This contrast is due in the 

 first place to the strong accumulations of saline water in the subtropics, but in these 

 layers it is also reinforced by the inflow of highly saline water from the Mediter- 

 ranean through the Straits of Gibraltar. Everywhere in this area there exists a well- 

 defined maximum in the vertical sahnity distribution at 1300 m (at about 20° N.) 

 lowering to 2500 m (at 35° S.) that must be attributed to the spreading of the 

 Mediterranean water. This effect of inflow from the European Mediterranean can 

 be seen particularly on the salinity chart for 1000 m depth. The spread of this type 

 of water will be discussed in greater detail later on (Vol. I, part 2, Chap. XVI, 3). 



The nature of the water beneath the upper part of the stratosphere in the Atlantic 

 indicates an area of formation in higher northern latitudes (north of 50° N.) in the 

 Western Trough. Here it is formed at the surface during the late autumn and early 

 winter, sinks by thermo-haline convection to great depths and spreads out more or 

 less horizontally below 2000-2500 m to fill the lower part of the stratosphere. The 

 high oxygen content which characterizes this water type will be discussed later in 

 connection with the oceanic circulation (see Vol. I, part 2, Chap. XX, 7. 



A similar contrast between the higher latitudes of both hemispheres is also present 

 in oceanic stratosphere of the Indian Ocean. Here it is due in the first place to the inflow 

 of highly saline water from the Red Sea. Coming from the Straits of Bab-el-Mandeb 

 (seep, 182 and Fig. 84), it sinks to about 10(X)m, mixes with less saline water in the Gulf of 



