14C, production

It is expected that due to the short residence time of Be and Cl in the atmosphere, 10Be and 36C1 measurements on ice cores will directly reveal isotope production variations. Due to dilution in the C02 exchanging system the atmospheric 14C/C-ratio shows a dampened response to 14C production rate variations. In contrast to the noble gas radioisotopes the size of the effective dilution reservoir - atmosphere plus parts of the ocean and biosphere - depends on the characteristic... 

For the following we assume that the atmospheric variations in C02 and in its carbon isotopic composition are entirely due to atmospheric system disturbances, such as the input of 14C-free C02 from fossil C02 production, and deviations from the average rate of 14C production by cosmic radiation. The system dynamics, i.e., the exchange coefficients and the eddy diffusivity are kept constant. We approximate the fossil C02 input p(t) by... 

We attribute the long-term and short-term 14C variations to cyclic variations in the 14C production rate Pi4 (t) which are... 

Using the actual C02 production history, Oeschger et al., [26] calculated for the Suess effect in 1950 a value of -2.0 percent. This is essentially in agreement with the measurements [44], though 14C fluctuations due to 14C production rate variation make a precise determination of the Suess effect difficult. 

Note that this approach assumes Fl4C = 1.0 and is constant prior to 1950. Actually the 14C/12C of atmospheric C02 did vary with time prior to 1900, mostly reflecting changes in the rate of 14C production in the upper atmosphere. During the Holocene, these variations were less than 10%, and they are documented in the calibration data sets based on 14C measured in known-age wood. Between 1900 and 1950, Eatm declined due to the addition of 14C-free C02 derived from fossil fuels, known as the Suess effect. Modeling of turnover times should use the actual atmospheric 14C inputs to photosynthesis, although it is not as important before 1959 as after. 

Total 14C product from 0.01 M cyclopropane-14C in the presence of O.OlAf solute. G(Product) approaches the limit — 0.85 at high electron scavenger concentrations. 

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