Upwelling history from northern Peruvian margin over the last 25 thousand years: A multi-proxy approach

Abstract:

In this study we present a compilation of multiproxy results focusing on the relationship between upwelling, primary production and the strong oxygen minimum zone (OMZ) over the last 25 thousand years in the Peruvian upwelling area. Sediment core M77/2-52-2 was obtained from the northern part of continental slope at 1250 m water depth outside the main OMZ. We combined results of surface productivity indicators such as organic carbon and biogenic opal as well as isotope proxies (δ¹⁵N_sed, δ³⁰Si_diatom) together with the diol upwelling index and biomarkers to decipher the changes in phytoplankton community in the surface ocean. In addition, we applied three independent biomarker-based SST proxies (U^K₃₇, TEX^H₈₆, LDI) to investigate SSTs and the response of these proxies to upwelling and oxygen dynamics. Overall, surface primary productivity was lower during the Last Glacial Maximum and gradually increased during the deglaciation causing bottom water deoxygenation indicated by both benthic foraminifera and δ¹⁵N_sed results. Organic SST proxies and biomarkers, together with biogenic silica and δ³⁰Si_diatom revealed a potential influence of upwelling strength and nutrient availability on these SST proxies and phytoplankton community changes.