Bomb radiocarbon in the Pacific: Annual and seasonal timescale variations

A time-stepped, multi-box model calculation is made to describe bomb radiocarbon distributions in the tropical Pacific, and hence to determine the influence of the South Equatorial Current flow on the chemistry of the central equatorial Pacific. The annual model results show that radiocarbon is influenced to a minor extent by this lateral flow, in agreement with previous studies. However, the seasonal version of the model reveals that the South Equatorial Current flow varies by a factor of 2-3 in order to explain the seasonal variations in bomb radiocarbon. Meridional geostrophic convergence and transequatorial Ekman transport from summer to winter hemisphere alone are not sufficient for defining the observed seasonal signals.