A strong influence of the mid-Pleistocene transition on the monsoon and associated productivity in the Indian Ocean

Abstract

The short-term variability in the Indian monsoon is well documented through instrumental records and paleoclimatic studies of the recent geological past.However, the effect of mid-Pleistocene transition (MPT) on the Indian monsoon has not been discussed extensively due to the scarcity of long-term records of changes in monsoon strength.We have used a 1.45 myr record of planktic foraminifera assemblages from the Site U1446 to understand the effect of the MPT on monsoon and associated processes.From the variability in the abundance of the summer monsoon assemblage, it is evident that the Indian summer monsoon (ISM) was stronger during the warm interstadials and weaker during the stadials, whereas the winter monsoon assemblage suggests a weakened winter monsoon during the interstadials.From the variation in eutrophic assemblage, it is inferred that, throughout the studied interval, productivity was controlled by the ISM.We report a large-scale reorganization of the Indian monsoon system after the onset of the MPT, which resulted in the strengthening of ISM.We also report that during the post MPT period, the summer monsoon was influenced by the 23 kyr precession cycle and the 100 kyr eccentricity cycle strongly modulated the winter monsoon.