77?^ Sea-nater and its Physical and Chemical Properties 81 



does not extend over the whole surface. More recent investigations have shown that 

 measurable variations occur, though they tend towards equilibrium. To investigate 

 more closely the direction of variations in the carbon dioxide content of the atmosphere 

 from equilibrium with that of the sea, and the mutual interaction of the two, it is 

 necessary to know: (1) the nature of the factors causing changes in the carbon dioxide 

 content in both spaces; (2) the distribution of the carbon dioxide in both media when 

 equilibrium has been finally established; and (3) the duration of the exchange process 

 leading to a new equilibrium and, dependent on that, the extent to which the sea and 

 the atmosphere come into contact enabling equalization of the differences between 

 them. 



As far as the first point is concerned, the principal source of the changes in the 

 carbon dioxide content appear to lie in the atmosphere. Goldschmidt (1934) has 

 given a general carbon dioxide budget for the atmosphere and the sea which is of 

 fundamental importance for the present problem. Table 32 shows the amounts of 

 carbon dioxide in y (=0-001 mg) per cm^ of the total surface of the Earth entering 

 or leaving the atmosphere and the sea annually. "Juvenile" carbon dioxide enters 

 the atmosphere from volcanoes, fumaroles and carbonated spring water. The value 

 given in Table 32 is the order of magnitude of the steady supply that would give the 

 total amount released during the course of geological history. In more recent times 

 there has been a particularly large increase in the amount of carbon dioxide entering 

 the atmosphere due to the steadily growing combustion of coal and oil by man. 



Compared with this large addition of carbon dioxide the amount removed from the 

 cycle by weathering processes and by the formation of carboniferous sediments is 

 very small. All these processes are, however, greatly exceeded by the amounts of 

 carbon dioxide involved in the biological processes of assimilation and respiration. 

 These two processes appear very largely to balance each other. The combustion of 

 coal by man can, however, as shown in Table 32, produce in time a measurable change 

 in the carbon dioxide contents of the atmosphere and the ocean, in spite of its small 

 annual effectiveness. 



Table 32. Annual budget of carbon dioxide per square centimetre of the 



Earth's surface 

 (After Goldschmidt, 1934) 



f juvenile COg 3-6 y 



Supply by -^ industrial combustion of coal and oil 800 y 



l^respiration and decomposition Approx. 40,000 y 



r photosynthesis Approx. 40,000 y 



Consumption by ^ weathering processes 3-4 y 



l^the formation of carboniferous sediments 0-3-2 y 



The addition of 0-0008 g/cm^ over a period of 35 years (1900-35) would give an 

 increase in the carbon dioxide content of the atmosphere of 0-028 g/cm- provided that 

 all this carbon dioxide remained in the atmosphere. A more recent and somewhat 

 more detailed presentation of the carbon dioxide cycle in the atmosphere, the hydro- 

 sphere and the lithosphere has been given by Lettau (1954) and is shown in Fig. 43a. 

 This gives detailed information on the individual parts of these interchanges and shows 



