Affiliations: [a] Department of Geology, Centre of Advanced Studies, Delhi University - 110007, India | [b] Marine Stable Isotope Lab, National Centre for Antarctic and Ocean Research, Vasco-da-Gama, Goa - 403804, India | [c] Geosciences Division, Physical Research Laboratory, Navrangpura, Ahmedabad, India
Abstract: Both the southwest monsoon (SWM) and the northeast monsoon (NEM) winds are responsible for the variations in the biological productivity in the western Arabian Sea (WAS), as recorded in the Arabian Sea sedimentary planktic foraminiferal record. While most earlier studies from this region ascribe the total observed variability predominantly to SWM, here we attempt to differentiate between the two monsoons based on the relative abundances of depth stratified planktic foraminifera assemblages. We observe a number of intervals of enhanced SWM. The first intensification (SWMI-I) occurred during ~16 to 12 ka and is possibly an outcome of early deglacial melting and stepwise increase in SWM strength after the end of the last glacial maximum (LGM). The second intensification (SWMI-II) is recorded at around ~10 ka, after the gradual strengthening from the end of the Younger Dryas cold episode. The last interval of intensification (SWMI-III) occurred around (~8.2 to 7.8 ka). In addition, there are two intervals of enhanced NEM: NEMI-I at around 19 to 17 ka and NEMI-II (~8.0 to 5.4 ka). These intervals of two enhanced NEM and three SWM wind strengths are bridged by decline in the SWM at different intervals, such as SWMD-I (~17 to 16 ka), SWMD-II (~12 to 11 ka) and SWMD-III (9.7 ka to 8.2 ka).
Keywords: Southwest monsoon, Northeast monsoon, Planktic foraminifera, Holocene, Last Glacial Maximum
