The Sea-)\'ater and its Physical and Chemical Properties 



85 



The mean vertical distribution of calcium carbonate in the Atlantic between 

 20° N. and 20" S. is shown in Fig. 44 from the results of 236 determinations made 

 during the "Meteor" Expedition. The variations in calcium carbonate content can be 

 divided into two groups: (1) Those due to differences in the total salinity — the alka- 

 linity and therefore the calcium carbonate both increase with increasing salinity; 



CaCojmg/l. 



CoCojg/kg Solt 

 3-32 3-36 3-40 3 44 348 352 



1000 



2000 



^ 3000 



4000 



5000 



Fig. 44. Mean vertical distribution of salinity (S^/q^, calcium carbonate (mg per litre of 

 water) and calcium hydroxide (in g per kg of salts). The last curve gives a measure of the 

 deviation of the calcium hydroxide content from proportionality with the salt respective to 



chlorine contents. 



(2) Those caused by chemical and biological changes. To show the last more clearly the 

 calcium content is given not in terms of unit volume of water but in unit weight of 

 salt; these are therefore expressed in g CaCOg per kg of salt or as per mill (%o). This 

 then shows the variations in the calcium carbonate content of sea- water from propor- 

 tionality with the salinity or the chlorinity. These are particularly important; they are 

 furthest from normal at two places: (1) in the surface layers close to the atmosphere; 

 (2) in the layer immediately above the sea bottom. The relatively small calcium car- 

 bonate content of the very surface layer must be attributed to consumption by plank- 

 ton, while the sharp increase at the sea bottom must be due to calcium carbonate 

 dissolving from the sediments at the bottom. 



The normal calcium content of the water in the open ocean can be taken as about 

 3-40 g CaCOg per kg of salt. The depletion of calcium carbonate in the surface layer 

 is about 2% and the enrichment at about 50 m above the bottom is about 4%. 

 Special measurements would be needed to determine whether there is ii further in- 

 crease nearer the bottom. The maximum value in the bottom water is not the same 

 everywhere. It appears to be larger the greater the depth of the bottom, as is shown in 

 Table 35 (Wattenberg, 1931). 



At depths of 3000 m this increase begins at about 300 m above the bottom, at 

 4000 m depths at 600 m and at 5000 m depths at about 1000 m. There are two fac- 

 tors involved in producing this apparently stationary state: (1) the continuous upward 

 flux of the calcium carbonate content as specified above ; and (2) the advective transport 



