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

Pavan Miriyala,V Ramaswamy,Tyson Sebastian,B Vijayagopal,N P Sukumaran,P B Ramamurty,A V Sijinkumar,B Nagender Nath

doi:10.1038/srep44310

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, 87Sr/86Sr for degree of weathering and 143Nd/144Nd 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 (δ18Osw-salinity changes of Northern Indian Ocean, effective Asian moisture content and δ18O records of Chinese caves) and are synchronous with changes in summer insolation at 30°N and δ18O of GISP2 implying that chemical weathering was not a later amplifier but worked in tandem with global climate change.

Highlights

Indian Ocean, that the chemical weathering responds to deglacial to mid-Holocene summer monsoon intensification in the Myanmar watersheds
A single record of weathering is available for this area which covers a long period (~280 ka12) but with a low resolution (~8 data points covering the time period presented here) which preludes the study of weathering changes in response to multiple climatic events occurred since the Last Glacial Maximum (LGM)
As shown in later part of the paper, 15-7 ka is the period of increased monsoon and associated with intensified chemical weathering

Summary

Introduction

Indian Ocean, that the chemical weathering responds to deglacial to mid-Holocene summer monsoon intensification in the Myanmar watersheds. At the current rate of anthropogenic emissions and increased atmospheric CO2 and temperature, it was estimated that the CO2 consumption flux related to weathering processes increases by more than 50% for an atmospheric CO2 doubling by the end of this century[4]. In this context, paleoweathering records of climate change regime would be useful to assess their linkage. A single record of weathering is available for this area which covers a long period (~280 ka12) but with a low resolution (~8 data points covering the time period presented here) which preludes the study of weathering changes in response to multiple climatic events occurred since the Last Glacial Maximum (LGM). Past salinity and paleoceanographic variations were already elucidated[13] for the new weathering record presented here

Methods

Results

Conclusion