El Niño‐Southern Oscillation related fluctuations of the marine carbon cycle

We investigate the response of a three‐dimensional ocean circulation model (Hamburg LSG) coupled on‐line with an oceanic carbon cycle model (HAMOCC‐3) to El Niño‐Southern Oscillation (ENSO) induced fluctuations of the wind field. During El Niño 1982/1983, when upwelling and biological productivity in the equatorial Pacific were strongly reduced and sea surface temperatures were increased, the oceanic CO 2 partial pressure in this region decreased significantly. Consequently, in 1982/1983 the CO 2 flux from the tropical ocean into the atmosphere was reduced. However, in 1983 the interannual deviations from the long‐term trend in atmospheric CO 2 showed in January low and in December high values with a total shift by more then 1.4 GtC. The model simulation supports the oceanic measurements and predicts a temporary uptake of 0.6 GtC during the ENSO year 1983. We conclude that the concurrent release of CO 2 from the land biosphere must have been about 2 GtC.