Surface waters are cooled in the autumn (October and November), while 

 in winter the whole column of water acquires a near-zero temperature. In 

 mid-winter conditions the temperature falls to freezing point and ice begins 

 to form on the surface. 



Ice conditions 



Water usually begins to freeze in the northern part of the Sea at the end of 

 November, and two or three weeks later in the southern part. At first ice 

 forms near the shores and the northern inlets freeze up ; then the whole of the 

 Maloe More and the eastern shores freeze. The open part of the Bolshoe More 

 is usually free of ice. Ice does not finally disappear until the second half of 

 April. 



Salinity 



As has been mentioned above, the salt composition of the Aral Sea differs from 

 that of ocean waters, even more than do those of the Caspian Sea, and as 

 regards the ratio of individual salts it approximates to fresh water {Table 279). 



Sodium, magnesium and calcium, and among the compounds sodium 

 chloride (54 per cent), magnesium sulphate (26 per cent) and calcium sulphate 

 (15 per cent) are preponderant in the Aral waters. 



The average salinity of the Aral Sea is about 10% o (Fig. 305). A fall of 

 salinity is observed in the mouths of the rivers, while in the inlets of the south- 

 eastern part of the Sea salinity rises to 14% as a result of intense evaporation. 

 A state approaching homohalinity is established in winter and spring ; in the 

 summer the surface waters lose some of their salinity. 



A forecast of the change of salinity of the Aral Sea associated with a pos- 

 sible future decrease of incoming river water and a fall of sea-level has been 

 made by L. Blinov (1956). The relationship of average salinity to sea-level 



