South Central Surface Water is located on the western Bide of 

 the ocean "between 23° and i|0°S latitude and is under the Influence 

 of wind from' the northeast which is 1 to 3° cooler than the water. 

 The water temperature varies between 26*^ and 20°C in a north to 

 south direction in February and between 21° and 15°C in August. 

 The degree of evaporation in this region markedly exceeds the pre- 

 cipitation which leads to a considerable increase in salinity. The 

 salinity is 35-0 to 36' 5 ^ and the dissolved oxygen is 4.27 to 4.93 

 ml/l. 



South Temperate Surface Water is found between 40 and 50°S 

 latitude in the western part of the ocean and between 35 and 55°S 

 latitude in the eastern part. It comes into the Indian Ocean from 

 the Atlantic in the stream of the West Wind Drift. Cyclonic atmos- 

 pheric conditions in this zone lead to increased precipitation which 

 results in a marked freshening of the surface water. The air temper- 

 ature, except in the northern part, remains higher than the water 

 temperature over the greater part of the year. The temperature in 

 the layer to 200 meters varies between 15° in the north to 5°C in 

 the south in August and between 20 and 7°C in February. The salinity 

 decreases from 35-0 %o to 33' 8 %o from north to south and the oxygen 

 content increases from 6. 22 to 8. 30 val/l. 



Subsurfa ce Water. Immediately below the surface waters there is a 

 layer called the subsurface water which extends to about 5OO meters 

 over most of the ocean and in individual regions (western subtropical 

 part) it reaches 60O - TOO meters. 



The subsurface water of the southern Indian Ocean is called 

 Indian Ocean Central Water. This water is believed to be formed by 



53 



