Last deglaciation changes in the equatorial upwelling system

Abstract

Last deglaciation in the Eastern Equatorial Pacific Ocean involved an intense reorganization of the upwelling system with the consequent changes in the nutrient budget, phytoplankton ecology and carbon fluxes towards the deep ocean. A multi-proxy study from ODP site 1240 provides a very complete insight on the time evolution of these changes. Sea surface temperature reconstructions based in both G. ruber-Mg/Ca ratios and alkenones show a strong seasonal gradient during this period induced by precession-driven changes in insolation. Thermocline records based in N. dutertrei chemistry support an enhancement of the upwelling system during this period. The combined study of molecular biomarkers indicate a significant change in the main phytoplankton producers along this period which is associated to a change in water fertilization processes, first by atmospheric iron deposition followed by the arrival of nutrient enriched undercurrent waters. The arrival of Antarctic source waters enriched in silicic acid during this period is further supported by the study of Nd isotopes