39 



have been used interchangeably. For this reason and also to 

 avoid confusion with the terms used in dealing with the open 

 ocean, the terra water unit is introduced, better to describe 

 the detailed classification of the water in Santa Monica Bay. 

 Where further subdivision is necessary, the terra sub - unit 

 will be used (Table I). 



The principal body of water which overlies the Santa Monica 

 shelf has been named the Shelf Water Mass. Its characteristics 

 are an essentially uniform salinity of about 33.5 o/oo and 

 temperatures ranging from 48° to 73°F, depending on season and 

 depth. Its character and T-S relationships are shown in Figure 

 12, which is a cumulative temperature-salinity diagram for the 

 waters of Santa Monica Bay. 



Below the Shelf Water Mass lies a layer of somewhat 

 different characteristics, here named the Slope Water Mass. 

 This water ranges in temperature from 46° to 50°F, and in 

 salinity from 33.6 o/oo to 34.3 o/oo. 



The deepest water present in the vicinity is here termed 

 the Basin Water Mass. It exhibits an essentially uniform 

 salinity below the depth of the sill of the Santa Monica Basin. 

 This water mass is characterized by an average temperature of 

 43°F and salinity of 34.3 o/oo. 



Within the Shelf Water Mass are two distinct water units, 

 separated primarily by temperature discontinuities or thermo- 

 clines. The Surface Water Unit includes the layer in which 

 the greatest seasonal temperature changes occur. It lies 

 above the thermocline and above such gradients in salinity 

 as do exist in the shelf water. The more uniform lower portion 



