Early deglacial (~19-17 ka) strengthening of the Northeast monsoon

Abstract

Earlier studies that mostly relied on bulk ¹⁴C dating indicated a weaker Southwest monsoon (SWM) and a stronger than present Northeast monsoon (NEM) during the Last Glacial Maximum (LGM, ~18000 ¹⁴C years or ~21000 calendar years ago). We have analyzed a sediment core from the equatorial Indian Ocean, where planktonic foraminifera were dated by Accelerator Mass Spectrometry (AMS ¹⁴C). δ¹⁸O analysis of three species of foraminifera viz. Globigerinoides ruber, Globigerinoides sacculifer, and Globorotalia menardii reveals that the NEM strengthened during the early deglacial period (~15000 ¹⁴C years ago or ~18000 calendar years ago) relative to the present and not during the LGM as surmised earlier.