Surface and thermocline ocean circulation intensity changes in the western Arabian Sea during ∼172 kyr

The relationship between monsoon-induced productivity and ocean circulation over millennial timescales is crucial. However, a study regarding the circulation of the western Arabian Sea (WAS) needs to be conducted. Understanding the seasonal, surface, and thermocline ocean circulation throughout the glacial-Interglacial period in the WAS is also elusive and essential. The long distant Antarctic Intermediate Water (AAIW) flow, and Sub-antarctic Mode Water (SAMW) penetration to the north side of the equator in the Indian Ocean needs to be understood and underlined using the micropaleontological (planktonic foraminiferal assemblages) and geochemical analysis such as oxygen isotope of Globigerinoides ruber and Neogloboquadrina dutertrei (δ18OG.ruber and δ18ON.dutertrei) in this study. Furthermore, understanding the variations in paleoproductivity, upper oceanic water column stratification, surface mixing, and thermocline layer variability in the WAS is also helpful. According to the results, the variation in the upwelling intensity during Glacial-Interglacial and monsoon variation suggest the upper water stratification/vertical mixing in the WAS. Here, we provide new evidence of poorly ventilated water mass in our region. Our results indicate that enhanced northward expansion of AAIW coincides with the weakening of summer monsoon during glacial periods except mid-MIS4, reflected by isotopic study and assemblages. In this context, depleted δ18ON. dutertrei value and high concentration of Globorotalia menardii (G. menardii) were due to lack/absence of AAIW ventilation and SAMW; therefore, warming occurred in the mid-MIS4. [Display omitted] •Mid-MIS4 warming enhanced the upwelling in the WAS as evident by assemblages and oxygen isotope records.•The weak intermediate ocean current circulation of AAIW and SAMW to the WAS during mid-MIS4 was responsible for the poor ventilation towards upper thermocline.•The glacial period (MIS6) is showing highest degree of stratification as evident by dominance presence of mixed-layer oligotrophic species and decreased relative abundance of mixed-layer eutrophic species.•Moderate winter convective mixing occurred during MIS2 as compared to MIS6.•Deepening of thermocline under thickening of mixed layer during interglacial periods (MIS5 & 1) and vice-versa during glacial period (MIS6).