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.
In a new study published in the journal Geology, Zhang et al. 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. Their results, with supporting evidence from other records, indicate significant mid-Pliocene Asian monsoon intensification, preceding the initiation of NHG at about 2.7 million years ago. The correlation between the monsoon record and marine calcium isotopes indicates that the 1.4-million-year-long monsoon intensification probably enhanced Asian continental erosion and chemical weathering.
Elevated chemical weathering and organic carbon burial probably lowered the contemporary atmospheric CO2, and the CO2 drop may have triggered the NHG onset as suggested by a recent study. As opposed to previous studies, here Zhang et al. propose a low-latitude-driven NHG glaciation scenario.
- Yi Ge Zhang, Junfeng Ji, William Balsam, Lianwen Liu, and Jun Chen. Mid-Pliocene Asian monsoon intensification and the onset of Northern Hemisphere glaciation. Geology, 2009; DOI: 10.1130/G25670A.1
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