Monsoon-Enhanced Silicate Weathering as a New Atmospheric CO2 Consumption Mechanism Contributing to Fast Late Miocene Global Cooling

Abstract

Fast late Miocene global cooling since ∼7 Ma accompanied by less changeable atmospheric CO2 levels revealed by existing proxy reconstructions has suggested an intriguing tectonic-climate link that remains controversial. Here, we present late Cenozoic clay mineral records of the silicate weathering intensity from the Chinese Loess Plateau and northeastern Tibetan Plateau to demonstrate a remarkable increase in silicate weathering intensity at ∼9–7 Ma induced by enhanced monsoon. This change caused CO2 consumption ranging from 0.18 to 1.8 × 1011 mol C yr−1 over the East Asian monsoon region, accounting for 0.2%–2% of the modern continental silicate weathering flux, thus providing an additional atmospheric CO2 sink. Moreover, we propose that this additional sink may have contributed to the large atmospheric CO2 consumption and fast global cooling in the late Miocene, which ultimately caused the onset of the Northern Hemisphere glaciation at ∼7 Ma.