INTRODUCTORY 



11 



or melting ice the surface salinity may be much less, for example in semi- 

 enclosed areas such as the Baltic Sea and Gulf of Bothnia, where surface 

 salinities may fall to 5% or less. On the other hand, in partially isolated 

 regions such as the Red Sea, where temperatures are high and evaporation 

 excessive, salinities may exceed 41 % . 



Certain general features of salinity distributions may be noted. Surface 

 salinities, on the average, reach a maximum around latitudes 20°N. and 

 20 C S. Salinities tend to be low in high latitudes due to low temperatures 

 and little evaporation. The range is less for intermediate and deep waters 



2 4 6 8 10 12 14 16 IS 20 22 



Chlorinity (°/oo) 



Fig. 1.4. Curve Relating Chlorinity to Chlorosity 



than at the surface, which is more directly affected by evaporation and 

 precipitation. Values for deep waters generally lie between 34-5% and 

 35% ; exceptions are the Red Sea and Mediterranean where deep waters 

 of high salinity are found. Charts showing surface salinities and lines of 

 isohalinity over the oceans of the world may be found in standard text- 

 books of oceanography. 



Minor Constituents. Besides the major constituents shown in Table 1.1, 

 sea water contains small amounts of some forty other elements, apart from 

 dissolved gases (22, 35a). The more important of these are silicon, 

 phosphorus, nitrogen, iron, manganese, copper and vanadium. The con- 

 centrations are very low, 7 mg kg or less (Table 1 .2). 



Some of these minor constituents, despite their low concentrations, are 

 necessary for the continued existence of all organisms. Phosphates and 



