Influence of atmospheric circulation on regional 14CO2 differences

Detailed analyses of published C-14 data from tree rings and atmospheric CO2 samples for the northern tropics in Asia (India, Thailand, and Vietnam) and Africa (Ethiopia) have been performed for the heavily bomb-influenced period 1963-1967 A.D. The results show that the Asian summer monsoon and Intertropical Convergence Zone (ITCZ) position influenced atmospheric (CO2)-C-14 over the study area. Similar analyses of atmospheric records for northern and western Europe, northwestern Africa, and the northeastern United States and tree ring data for east Asia show that the Northern Hemisphere distribution of bomb C-14 for 1963-1967 depended on atmospheric circulation controlled by the seasonal positions of Hadley cell boundaries and the ITCZ. The distribution of C-14 did not have a simple latitudinal dependence. This work shows that the seasonal atmospheric circulation patterns are crucial for the description of atmospheric C-14 gradients during the bomb peak period. These principles can be applied to the interpretation of the small intrahemispheric C-14 offsets of the remote past.