Articles | Volume 12, issue 3
Research article
31 Mar 2016
Research article |  | 31 Mar 2016

Terrigenous material supply to the Peruvian central continental shelf (Pisco, 14° S) during the last 1000 years: paleoclimatic implications

Francisco Javier Briceño-Zuluaga, Abdelfettah Sifeddine, Sandrine Caquineau, Jorge Cardich, Renato Salvatteci, Dimitri Gutierrez, Luc Ortlieb, Federico Velazco, Hugues Boucher, and Carine Machado

Abstract. In the eastern Pacific, lithogenic input to the ocean responds to variations in the atmospheric and oceanic system and their teleconnections over different timescales. Atmospheric (e.g., wind fields), hydrological (e.g., fresh water plumes) and oceanic (e.g., currents) conditions determine the transport mode and the amount of lithogenic material transported from the continent to the continental shelf. Here, we present the grain size distribution of a composite record of two laminated sediment cores retrieved from the Peruvian continental shelf that record the last ∼ 1000 years at a sub-decadal to centennial time-series resolution. We propose novel grain size indicators of wind intensity and fluvial input that allow reconstructing the oceanic–atmospheric variability modulated by sub-decadal to centennial changes in climatic conditions. Four grain size modes were identified. Two are linked to aeolian inputs (M3: ∼ 54; M4: ∼ 91 µm on average), the third is interpreted as a marker of sediment discharge (M2: ∼ 10 µm on average), and the last is without an associated origin (M1: ∼ 3 µm). The coarsest components (M3 and M4) dominated during the Medieval Climate Anomaly (MCA) and the Current Warm Period (CWP) periods, suggesting that aeolian transport increased as a consequence of surface wind stress intensification. In contrast, M2 displays an opposite behavior, exhibiting an increase in fluvial terrigenous input during the Little Ice Age (LIA) in response to more humid conditions associated with El Niño-like conditions. Comparison with other South American paleoclimate records indicates that the observed changes are driven by interactions between meridional displacement of the Intertropical Convergence Zone (ITCZ), the South Pacific Subtropical High (SPSH) and Walker circulation at decadal and centennial timescales.

Short summary
Comparison between records reveals a coherent match between the meridional displacement of the ITCZ-SPSH system and the regional fluvial and aeolian terrigenous input variability. The aeolian input intensity and the anoxic conditions recorded by marine sediments showed a close link that suggests a common mechanism associated with SPSH displacement. Changes in sediment discharge to the continental shelf are linked to the southward displacement of the ITCZ-SPSH and Walker circulation.