176 



Salinity of the Ocean, its Variation in Oceanic Space and in Time 



is the velocity of the horizontal advection. At the right-hand (northern) boundary 

 there is at the same time an outflow of 5 X 10* X m-^-i x 10"-^ g of salt from the entire 

 volume so that the loss of salt in g/sec will be 50u{si — s). For a stationary salinity 

 distribution this loss must be compensated by a gain due to mixing, that is by 

 1-0 X 10"' g/sec. Taking u equal to 5 cm/sec, this is only possible for a horizontal 

 salinity gradient of(si — s) = 4 x 10^^° %o/cm in the current. The salinity at 7000 km 



450 m 



= 0-12 MO" 



(vertical gradient 

 of salt at 450m) 



950 m 



I cm 



068 X 10 g 



Inc rease 



of 



salt content 



1-00 X lO'^g 



pro sec 



salinity S 

 velocity U 



salt flux 



Fus« 10" 



I 



Fus, « 10 



— ^ = 0-08 1 10 

 Az 



(vertical gradient 

 of salt at 950m) 



0-32 « 10 g 



salt loss 

 Fu X I0''(s,-s) 



Fig. 80. Salinity exchange and advection. For w = 5 cm/sec results salinity gain = salinity 

 loss: 5 X 10* X 5 X 10-^ (s^ - s) = 2-41 x 10"^ or {s^ - s) = 0-97 x 10-» "/oo per centi- 

 metre. 



distance in the core of subantarctic intermediate water is 34'34%o, at 9000 km, however, 

 34-42%o, so that according to the observed values there is a salinity gradient of 0-08%o 

 for the 2000 km = 2 x 10^ cm. This gives exactly the value derived above of 

 4 X 10"^"%o/cm. The vertical and horizontal salinity distribution in the subantarctic 

 intermediate current at this point can thus remain stationary with values of 

 4 g cm~^ sec~^ for A and 5 cm/sec for u. The ratio 



Aj pu = t — 0'8 cm/sec 



satisfies therefore the condition of a stationary state of the phenomenon in time. It 

 is fairly easy to see that the above calculation gives only the quantity Ajpu and not the 

 absolute value of the individual quantities. 



