Increased chemical weathering during the deglacial to mid-Holocene summer monsoon intensification

Abstract

Chemical weathering and the ensuing atmospheric carbon dioxide consumption has long been considered to work on geological time periods until recently when some modelling and natural records have shown that the weathering-related CO2 consumption can change at century to glacial-interglacial time scale. Last glacial to interglacial transition period is a best test case to understand the interplay between Pco2 -temperature-chemical weathering when a pulse of rapid chemical weathering was initiated. Here we show, from a high resolution 54 ka record from the Andaman Sea in the northern Indian Ocean, that the chemical weathering responds to deglacial to mid-Holocene summer monsoon intensification in the Myanmar watersheds. The multi-proxy data (Al/K, CIA, Rb/Sr,87 Sr/86 Sr for degree of weathering and 143 Nd/ 144 Nd for provenance) reveal an increase in silicate weathering with initiation of interglacial warm climate at ∼17.7 ka followed by a major change at 15.5 ka. Inferred changes in chemical weathering have varied in tandem with the regional monsoonal proxies (δ18 O sw -salinity changes of Northern Indian Ocean, effective Asian moisture content and δ 18 O records of Chinese caves) and are synchronous with changes in summer insolation at 30°N and δ 18 O of GISP2 implying that chemical weathering was not a later amplifier but worked in tandem with global climate change.