Sources and burial of particulate organic matter in the Kuroshio mainstream and its response to climate change over the past millennium

Abstract

Sedimentation rate and biogenic elements of a sediment core KET-1 recovered from Kuroshio Mainstream, east of Taiwan, were determined to investigate variation of organic carbon burial and its response to climate fluctuations. The results showed that the organic carbon burial flux was mainly depended on the sedimentation rate and the input of river particles had a dilution effect on total organic carbon (TOC) content of the sediment. Based on the organic carbon burial flux, the entire depositional process could be divided into three stages, which exactly corresponded to three specific climate periods over the past millennium. During the Medieval Warm Period (MWP, ad 1150–1250), the strong East Asian summer monsoon (EASM) caused more river input to the sea, resulting in high sedimentation rate and high organic carbon burial flux, meanwhile the dilution effect of river particles as well as low marine primary productivity resulted in relatively low proportion of marine organic matter (MOM) in the sediment, which was reflected by low TOC content. During the Little Ice Age (LIA, ad 1400–1835), lower organic burial flux and higher marine primary productivity as well as higher TOC content in the sediment were accompanied by weakened EASM. In the Modern Period (MP, ad 1835–present), however, the correlation between organic carbon burial and climate fluctuations that was found to be significant during the MWP and LIA had been greatly changed, and anthropogenic forcing was thought to be the primary driving factor. Overall, the climate variability and anthropogenic activities over the past millennium dominated the organic carbon burial in the sediment along the Kuroshio mainstream.