<SUP>14</SUP>C in air over the Arabian Sea

Global monitoring of radiocarbon in atmospheric CO2 began during the mid fifties to determine the time scales of exchange of radiocarbon (and CO2) between the atmosphere and other terrestrial reservoirs. The distribution of natural radiocarbon in the environment was perturbed significantly during the 1960s through injection of 14C from nuclear weapon tests. This 'bomb 14C has proved to be an excellent tracer to characterize and quantify CO2 exchange between various reservoirs. We have measured radiocarbon activity of marine air over the central and eastern Arabian sea during 1993-95. The mean A 14C values are 121 ±6, 116 ±6 and 105±5%o respectively for these three years. These values, in conjunction with those reported in the literature for troposphere for the decades of 60s through 80s, show that the 14C activity in the tropospheric air has been decreasing exponentially with an e-folding time of -16 years