Radon-calibrated emissions of CO₂ from South Africa

Abstract

Atmospheric CO₂ and ²²²Rn have been monitored at Amsterdam Island since 1980. Data were selected in order to eliminate any local influence. Typical CO₂ concentrations of the subantarctic marine atmosphere can be determined by selecting those values for which ²²²Rn radioactivity was particularly low: less than 1 pCi m^-3. ²²²Rn concentrations higher than 2 pCi m^-3 are mainly due to injections into the subantarctic atmosphere from the continental source of South Africa. The passage of air masses under continental influence also shows typical CO₂ variations, well correlated with ²²²Rn variations. From the knowledge of the global continental fluxes of ²²²Rn, it has been possible to estimate CO₂ fluxes into the atmosphere from South Africa. The mean CO₂ flux corresponding to a 6-month period from May to October is about 5 millimole m^-2 h^-1. Continental CO₂ emissions reach a maximum in August.