168 



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



While the entire area between the behs of subtropical highly saline water in the 

 Northern and the Southern Hemisphere show these salinity maxima, just above or 

 inside the thermocline two belts without maxima stand out sharply; one between 10° 

 and 15° N, and extending from 45° W. eastwards to the African continent and a 

 second, but more narrow belt, between 2° S. and 3° S. and extending from 30° to 10°, 

 which is particularly well developed in the central part of the Atlantic Ocean (see 

 Fig. 72). These two belts without salinity maxima more or less mark the southern 



Fig. 72. Distribution of salinity in the tropospheric salinity maximum in the subtropic and 



tropics of the Atlantic. 



and northern limit, respectively, of the subtropical water masses spreading towards 

 the equator. Between these two belts from about 7° N. to the equator the maximum 

 appears again and may be very pronounced. This is the region of the Equatorial 

 Countercurrent which is fed at a depth of 80-100 m from regions west of 35°-40° W., 

 which are situated outside the area with no maximum. The salinity maxima of the 

 tropics and the subtropics are thus very closely connected with the tropospheric 

 circulation in these areas. The best illustration of the formation, extent and intensity 

 of this very pronounced thin layer of high salinity lying between low salinity layers 

 (above and below) is given by a vertical cross-section along the core of the Equatorial 

 Countercurrent and the Guinea Current in the Atlantic Ocean. This section is shown 

 in Fig. 73. It starts in the central Atlantic at about 18° N., 37° W., proceeds south- 

 wards to 10° N., 38° W. and then along the core of the Equatorial Countercurrent, 

 finally reaching the inner Gulf of Guinea. The layer of maximum salinity spreads 

 southward from the homo-haline top layer of the subtropical North Atlantic below 

 the low salinity surface layer towards equatorial latitudes. If the 35-5%o isohaline is 



