222 DISCOVERY REPORTS 



Below the level of minimum temperature, the temperature increases to a maximum 

 value in the upper stratum of the warm deep layer, and the water in this stratum, 

 whatever its origin may be, has a component of movement southwards. Table IX 

 shows the depth of this maximum temperature in 30° W, together with the depth of 

 the maximum salinity in the warm deep layer. 



deep water in metres 



Depth of the maximum salinity of the 3400 2800 2650 2000 2000 20DO 



warm deep layer in metres 



The boundary between sub-Antarctic or Antarctic intermediate water and the 

 warmer layer beneath — that is to say the boundary between the north- and south- 

 going movements — may be regarded with sufficient accuracy as lying midway between 

 the levels of minimum and maximum temperatures. 



The following table shows the depth of this boundary in 30° W. 



Table X 



Latitude 45° S 40° S 35° S 30° S 25° S 20° S 15° S 10° S 5° S 



Depth of the boundary between sub-Ant- iioo 1500 i960 1980 1740 1550 1270 1250 1150 



arctic or Antarctic intermediate water, 



and warm deep water in metres 



The origin of the water in the Antarctic intermediate layer has been discussed by 

 Brennecke (1921, p. 140), who describes the movement in the layer as the sub-Antarctic 

 deep current ; he gives its origin as the surface drift out of the Weddell Sea, which sinks 

 in about 50" S and pushes its way, at an average level of about 1000 m., through the 

 South Atlantic Ocean as far as 25° N. The layer is also described by Drygalski (1927, 

 p. 498) who describes its origin as Antarctic polar water. Both descriptions are correct 

 although not complete. 



TEMPERATURE, SALINITY AND OXYGEN CONTENT OF 

 ANTARCTIC INTERMEDIATE WATER 



Although it has probable movements from west to east and east to west, the Antarctic 

 intermediate water flows northwards. This is proved by the fact that the layer which 

 extends as far north as 25 ° N in the West Atlantic contains water which can only have had 

 its origin south of 40° S. As the water flows northwards its properties change as a result 

 of the vertical mixing which takes place between the water in the layer and the waters 

 above and below it. The changes are greatest at the top and bottom of the layer where 



