The glacial evolution of the tropical Indian Ocean

The tropical Indian Ocean is a key component of the ocean-atmosphere system, due to the exchanges of large amounts of heat and moisture and the interactions with the Australasian Monsoon on a range of timescales. The evolution of the tropical Indian Ocean during the last several glacial-interglacial cycles remains less documented than its Atlantic and Pacific counterparts, limiting our understanding of the response of this critical sector of the ocean to global and regional climate change. Here we present a record that spans the last million years of upper ocean hydrography from the southernmost Bay of Bengal (International Ocean Discovery Program [IODP] Site U1443; 5°23.05’ N, 90°21.67’ E, 2,924 m water depth), based geochemical proxies (trace elements, stable oxygen and carbon isotopes) measured in surface and sub-thermocline planktic foraminiferal. We will centre on the evolution of the glacial temperatures during glacial climate states featuring different insolation, ice volume, and greenhouse gas concentrations, hence radiative forcing. Next, we will discuss the relationship of the tropical Indian Ocean temperature with the Indian monsoon winds and precipitation during both glacial periods and glacial terminations.