ENSO-like forcing on oceanic primary production during the Late Pleistocene

Late Pleistocene changes in oceanic primary productivity along the equator in the Indian and Pacific oceans are revealed by quantitative changes in na noplankton communities preserved in nine deep-sea cores. We show that varia tions in equatorial productivity are primarily caused by glacial-interglaci al variability and by precession-controlled changes in the east-west thermo dine slope of the Indo-Pacific. The precession-controlled variations in pro ductivity are linked to processes similar to the Southern Oscillation pheno menon, and they precede changes in the oxygen isotopic ratio, which indicat es that they are not the result of ice sheet fluctuations. The 30,000-year spectral peak in the tropical Indo-Pacific Ocean productivity records is al so present in the Antarctica atmospheric CO2 record, suggesting an importan t rote for equatorial biological productivity in modifying atmospheric CO2.