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DISCOVERY REPORTS 



and less saline water alternating with patches of cooler and more saline water. The oxygen 

 content of the water decreases towards the north as the oxygen is used up by animal 

 life and by oxidizable organic matter in the water. The decrease in oxygen content is also 

 approximately proportional to the distance the water flows, and it is not regular. There 

 are alternate patches of water with high oxygen content and low oxygen content. 



The irregularity in the increase in temperature and salinity, and in the decrease in 

 oxygen content, is partly due to the difference between the water which leaves the region 

 of intense mixing just north of the Antarctic convergence in winter, and that which 



LATITUDE 

 20° 10" 



34 10 



3420 



3470 



Fig. 22. The change in the saHnity and oxygen content towards the north in the 

 Antarctic intermediate current. 



leaves in summer. The mixture of waters in this region has its maximum temperature 

 and minimum salinity at the end of the summer. Both are the result of the higher 

 temperature and lower salinity of the Antarctic surface water which sinks in summer, 

 and it is to be expected that the mixture will have its maximum oxygen content at about 

 the same time. This will be so because the Antarctic surface water has its greatest 

 oxygen content in spring and early summer, when the phytoplankton is at its maxi- 

 mum, and also because there is probably a greater percentage of Antarctic surface 

 water in the mixture in summer than there is in winter when the surface currents are 

 slower. 



Fig. 22 shows the oxygen content and salinity of the water at the level of minimum 

 salinity in different latitudes in 30° W. To make comparison of the curves easier the 



