Provenance and climate changes inferred from magnetic properties of the sediments from the lower Yangtze River (China) during the last 130 years

Abstract

Abstract It is essential to have a clear scientific view on paleoclimate change and its potential environmental and socio-economic impacts for the prediction of future climate change. Fluvial sediment is one of the best archives for the investigations of high-resolution environmental variability and anthropogenic impacts on catchment over the last hundreds or even thousands years (Anthropocene). In this study, we examine magnetic properties of a 130-year fluvial sediment profile from an island in the main channel of the lower Yangtze mainstream, which aims to determine the connections between modern observational data and paleoclimate signals from sediments. Sediments from the upper Yangtze River is characterized by high concentration of magnetite, which is different from the middle reach. The difference of magnetic properties allows us to trace particles in the lower reach back to upstream of the Yangtze River. Climate change that reconstructed from physical properties of sediment (susceptibility and mean grain size) is comparable to those records in historical documents, which provides a possible way to obtain precise ages. The calibrated sedimentation rate reflects long-term variation of flood/drought events over the catchment, which is dominantly controlled by the climate circulation of Pacific. The enhanced human impacts since 1950s especially in the mid-lower reaches are observed. Therefore, riverine sediment not only contains paleoclimate information, but also reflects human activities.