STRATOSPHERIC CONTRIBUTION TO THE GLOBAL BOMB RADIOCARBON INVENTORY -MODEL VERSUS OBSERVATION

An attempt is made, through modeling, to account for the decline in th e C-14/C ratio in atmospheric CO2 after its bomb-test-induced peak in 1963. The model suggests that as of 1964 about one third of the bomb C -14 remained in the stratosphere and that it was released to the tropo sphere with an e-folding time of about seven years. By contrast, measu rements carried out in the stratosphere suggest that at that time the excess was closer to one quarter of the total and that the e-folding t ime for its decline was 3 +/- 1 years. The anomaly between model and o bservation cannot be attributed solely to an inadequacy in the represe ntation of the terrestrial biosphere. Rather, it must reflect either a n inadequacy in the ocean model or in the measured stratospheric inven tories.