R O G E R R E V E L L E A N D H A N S E. S U E S S 20 documented, may yield a far-reaching insight into the processes determining weather and climate. It therefore becomes of prime importance to attem t to determine the way in which carbon &oxide is partitioned between the atmosphere, the oceans, the biosphere and the lithosphere. The carbon dioxide content of the atmosphere and ocean is presumably regulated over geologic times by the tendency toward thermodynamic equilibrium between silicates and carbonates and their respective free acids, silica and carbon dioxide (UREY, 1952). The atmosphere contains and probably has contained during geologic times considerably more CO, than the equilibrium concentration (HUTCHINSON, 1954), although uncertainties in the thermodynamic data are too great for an accurate quantitative comparison. Equilibrium is approached through rock weatherin and marine sedimentation. Estimated rates o these processes give a very long time constant of the order of magnitude of IOO,OOO years. Rapid changes in the amount of carbon dioxide roduced by volcanoes, in the state of the Losphere, or as in our case, in the rate of combustion of fossil fuels, may therefore cause considerable departures from average conditions. P Table 2. Estimated present annual rates of some processes involving atmospheric and oceanic carbon dioxide, in part after HUTCHINSON (1954) I n units of atm CO,(AO) Consumption of fossil 0.0091 fuels-CO, produced. Bicarbonate and carbonate added toocean 0.00103 by rivers (as C 0 , ) l . . Photosynthesis on land 4 0 , consumed. . . . 0.073fo.01~ Photosynthesis in ocean -CO, consumed. . . . 0.46fo.3 0.0039 0.0004 the rate at which an excess amount of CO, in the atmosphere is absorbed by the oceans. The exchange rate of isotopically labeled CO, between atmosphere and ocean, which, in principle, could be deduced from C14 measurements, is not identical with the rate of absorp tion, but is related to it. Notations and geochemical constants In our discussion of exchange and absorption rates we shall use the following notations: Total carbon of the marine so: carbon reservoir at equilibrium condition, at time zero. Atmospheric CO, carbon at A, : time zero. Annual amount of industrial I: CO, added to the atmosphere. Time in years. t: Amount of CO, derived from s=S,-S0: industrial fuel combustion in the sea at time t. Amount of CO, derived from r = i t - s: industrial fuel combustion in the atmosphere at time t. Observed decrease in C14 acr* : tivity. Average lifetime of a CO, t(atm) : molecule in the atmosphere, before it becomes dissolved in the sea. Average lifetime of carbon in t(sea) : the sea, before it becomes atmospheric CO,. k, = I/t(atm) : Rate of CO, transfer per year from the atmosphere to the sea. k, = I/t(sea) : Rate of CO, transfer per year from the sea to the atmosphere. pco,: Partial CO, pressure in the atmosphere. 0.031 Table 3 gives the amount of carbon, expressed in CO, equivalents, in the various According to CONWAY (1942) and HUTCHIN- geochemical reservoirs on the surface of the SON (1954) 87 yo of the river borne bicarboEarth. nate and carbonate comes from weathering of The svmbols S* and A* shall be used for carbonate rocks, the remainder from weathering denoting respective “effective” reservoirs. of silicates. 0.20 The answer to the uestion whether or not the combustion of coa , petroleum and natural gas has increased the carbon dioxide concentration in the atmosphere depends in part upon 4 Rate of CO, exchange between sea and atmosphere Two types of C14 measurements independently allow calculation of the exchange rate Tellus IX (1957), 1