Excellent studies have been carried by Indian scientists to understand paleoceanographic changes in the Indian Ocean including the Arabian Sea and Bay of Bengal using Ocean Drilling Program cores. These studies revealed both short-term and long-term changes in the Indian Ocean circulation and Indian monsoon system. In general, summer monsoon was intense during warm intervals and weaker during cold intervals. Changes in deep-sea were also observed. The above studies were based on planktic and benthic foraminiferal faunal and geochemical data. Changes in deep sea oxygenation, oxygen minimum zone and surface productivity in the Indian Ocean including the Arabian Sea and Bay of Bengal during the Neogene and Quaternay were driven by the Indian summer monsoon. These changes in nutrient and oxygen levels drove major changes in the fauna and flora of the Indian Ocean. Indian monsoon variability has been suggested as contemporaneous with the southeast Monsoon variability during the last glacial and the Holocene.