Arun Deo Singh
Arun Deo Singh, is a Senior Professor of Micropaleontology and Paleoceanography at the Department of Geology, Banaras Hindu University (BHU), India. His current research interests include: understanding Global ocean-climate variability on tectonic, orbital to sub-orbital timescales; evolution of ocean gateways and its impact on ocean circulation and climate change; and the development of new micropaleontological proxies for paleoceanographic/ paleoclimatic reconstructions. Understanding the South Asian Monsoon variability and its atmospheric-oceanic teleconnections with high- and low- latitude climate components, is a key area of his research interest. His expertise also extends to investigating the evolution and dynamics of the oxygen minimum zone and its role in biogeochemical cycles. Participated in the IODP Expeditions 339 (Northeast Atlantic Ocean) and 355 (Arabian Sea). Currently, he is a member of INSA-SCOR (Scientific Committee on Oceanic Research) national committee.
Evolution and spatio-temporal variability of the Indian Monsoon system: Recent advances and outstanding issues.
Indian monsoon is a dynamic subsystem of the larger Asian monsoon system, driven by the annual cycles of solar insolation and ocean-atmosphere-land interactions. The Inter-Tropical Convergence Zone (ITCZ) modulated monsoon winds produce large-scale seasonal changes in ocean circulation, surface hydrography and biological productivity in the northern Indian Ocean. The Indian monsoon has two distinct seasonal components: the wet summer (or SW) monsoon, which contributes majority of the annual rainfall over the Indian subcontinent; and the dry and cold winter (or NE), monsoon that brings limited rain primarily to southeastern India. Multi-proxy reconstructions from the two northern Indian Ocean basins bordering the Indian subcontinent -Arabian Sea and Bay of Bengal (BoB)- have provided important insights into the Indian summer monsoon (ISM) variability on different timescales. However, most existing paleomonsoon records were derived from the dry, summer monsoon wind-dominated regions of the Arabian Sea. In recent years, the emphasis was given to develop more proxy records of summer monsoon associated precipitation/runoff from the BoB and western Indian margin, because previous studies showed a significant heterogeneity between summer monsoon winds and rains across the regions. Even though, major advancements in understanding the seasonal dynamics of ISM have been made; considerable uncertainties still remain with respect to the connections among monsoon-related variability recorded by different proxies such as, wind intensity, precipitation/runoff, marine productivity (nutrient availability) and the associated physical processes. Furthermore, our understanding of the evolution of Indian winter monsoon, and forcing and feedbacks that drive seasonal monsoon variability at different timescales remain elusive.
Here, we analyze and discuss multi-proxy records of surface hydrographic parameters (stratification, SST, SSS), upper water-column structure (mixed-layer and thermocline conditions), wind induced upwelling/vertical mixing and productivity, developed from three distinct oceanographic settings viz. eastern Arabian Sea (influenced by summer monsoon runoff in south and winter monsoon winds in north), western Arabian Sea (a region of intense upwelling during summer monsoon) and the northern Bay of Bengal (dominated by summer monsoon precipitation/river runoff). The integrated results provide new insights into the understanding of the basin-wide evolution of the upper water-column structure and inter-basinal water-mass exchange in response to seasonal changes in the monsoon circulation across the regions, at centennial-millennial timescales. By combining paleo-productivity records with SST and benthic carbon isotope data, we constrain the role of seasonal monsoon dynamics in driving the spatio-temporal variability and the possible role of Atlantic Meridional Overturning Circulation (AMOC) in nutrient supply. We also evaluate the role of southern hemisphere on the Indian monsoon dynamics by comparing our new records of ANN-derived SST and oxygen isotope of mixed-layer dwelling planktic foraminifera from the eastern Arabian Sea with temperature records of Southern Hemisphere ice-cores.
