EL-NINO-SOUTHERN OSCILLATION RELATED FLUCTUATIONS OF THE MARINE CARBON-CYCLE

We investigate the response of a three-dimensional ocean circulation m odel (Hamburg LSG) coupled on-line with an oceanic carbon cycle model (HAMMOCC-3) to El Nino-Southern Oscillation (ENSO) induced fluctuation s of the wind field. During El Nino 1982/1983, when upwelling and biol ogical productivity in the equatorial Pacific were strongly reduced an d sea surface temperatures were increased, the oceanic CO2 partial pre ssure in this region decreased significantly. Consequently, in 1982/19 83 the CO2 flux from the tropical ocean into the atmosphere was reduce d. However, in 1983 the interannual deviations from the long-term tren d in atmospheric CO2 showed in January low and in December high values with a total shift by more that 1.4 GtC. The model simulation support the oceanic measurements and predicts a temporary uptake of 0.6 GtC d uring the ENSO year 1983. We conclude that the concurrent release of C O2 from the land biosphere must have been about 2 GtC.