Abstract

The late Pliocene onset of major Northern Hemisphere glaciation (NHG) is one of the most important steps in the Cenozoic global cooling. Although most attempts have been focused on high-latitude climate feedbacks, no consensus has been reached in explaining the forcing mechanism of this dramatic climate change. Here we present a key low-latitude climate record, the high-resolution Asian monsoon precipitation variability for the past five million years, reconstructed from South China Sea sediments. Our results, with supporting evidence from other records, indicate significant mid-Pliocene Asian monsoon intensification, preceding the initiation of NHG at ca. 2.7 Ma ago. This 1.4-million-year-long monsoon intensification probably enhanced monsoon-induced Asian continental erosion and chemical weathering and in the process left fingerprints in marine calcium isotopes. Furthermore, increased rock weathering and/or organic carbon burial probably lowered the contemporary atmospheric CO2 and may have triggered the NHG onset.

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