Carbon dioxide exchange with atmosphere

Figure 3. A plot of calcium minus hydrogen concentration difference (open triangles) in units of millimoles per liter versus incident rainfall pH. Calculated points for solutions open (open circles) and closed (open squares) to exchange with atmospheric carbon dioxide, also shown, define the anticipated range of values.

The carbon dioxide content of seawater is determined in waters dose to the surface by exchange with atmospheric carbon dioxide. Plants consume CO2 in the process of photosynthesis. The solute carbon dioxide influences the balance of carbon-ate/hydrogen carbonate and thus the formation of lime deposits and covering layers. This balance is the basis for the buffering properties of seawater and its relatively high pH level. 

Keeling, C. D. (1973a). The carbon dioxide cycle. Reservoir models to depict the exchange of atmospheric carbon dioxide with the oceans and land plants. In "Chemistry of the Lower Atmosphere" (S. Rasool, ed.), pp. 251-329. Plenum Press, New York. 

The radiocarbon ratio also evolves very rapidly from its initial value of -50 to an average value of about -8 per mil. This evolution is not a consequence of evaporative concentration but, instead, of an approach to equilibrium with atmospheric carbon dioxide. Average surface seawater contains significantly less radiocarbon than does the atmosphere because its isotopic composition is affected by exchange with the deep ocean as... 

TABLE 2.1 Estimated Annual Global Carbon Dioxide and Carbon Exchanges with the Atmosphere ... 

---