Variation in the Indian Summer Monsoon intensity during the Bølling-Ållerød and Holocene

Variations in the Indian summer monsoon (ISM) intensity during the last 16.7 ka have been studied using organic carbon (Corg), δ15N of sedimentary organic matter, CaCO3, sediment texture, δ18OC and Mg/Ca derived sea surface temperature, δ18O of sea water and sea surface salinity, in a 14C-dated sediment core from the eastern Arabian Sea. The δ18O in water and planktonic foraminifera shells off the central west coast of India may be controlled by the ISM intensity as this area receives high precipitation and land runoff. Also, the Corg and CaCO3 contents of sediments and δ15N of sedimentary organic matter may be linked to ISM-induced productivity and denitrification. The results of the present study reveal that between 16 and 15.2 ka BP the ISM was weak with minor fluctuations and started intensifying around 15.2 ka BP, at the onset of the Bølling-Ållerød (B-A) event. The B-A event is characterized by higher water column denitrification rates comparable to the present day. The ISM signatures observed in the δ18OC record of B-A event compare well with those from Timta cave of the western Himalayas and also the Asian summer monsoon signatures from the Hulu caves in China and warming signatures in Greenland Ice Sheet Project 2 (GISP2) suggesting atmospheric tele-connections through Intertropical Convergence Zone (ITCZ). The boundary between the Younger Dryas and th