Measurements of gas exchange rates in nature

The distributions of both natural and bomb-produced radiocarbon in the ocean have been used to determine the mean global gas exchange mass transfer coefficient. The calculation based on natural radiocarbon assumes a steady-state mass balance between the production of in the atmosphere by cosmic ray spallation (see Chapter 5) and 

Using this formulation, the C02 fugacity in the atmosphere becomes 

The pre-industrial atmosphere and mean surface ocean/co values were within a few percent of being the same globally, so we will assume that/ Oj =/c o2- Now, substitutingEqs. (10.17) and (10.19) into Eq. (10.15) and combining it with Eq. (10.14) gives an expression for 

Since the diffusion coefficients of C02 and CO2 are about the same ( C02 diffuses 0.2% slower than C02), this is also the mass transfer coefficient for CO2. 

The pre-industrial atmospheric G/ G values, R, have been determined from radiocarbon measurements of tree rings, and the value of is based on hundreds of deep ocean DI G measurements, 

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