1. Introduction to the Indian Ocean 2. A brief historical overview of the maritime Indian Ocean world 3. Past, present, and future of the South Asian monsoon 4. Intraseasonal variability in the Indian Ocean region 5. Climate phenomena of the Indian Ocean 6. Extreme events and impacts in the Indian Ocean 7. Impacts of the Indian Ocean on regional and global climate 8. Indian Ocean circulation 9. Oceanic basin connections 10. Decadal Indian Ocean variability 11. Indian Ocean primary productivity and fisheries variability 12. Oxygen, carbon, and pH variability in the Indian Ocean 13. Nutrient, phytoplankton and zooplankton variability in the Indian Ocean 14. Air-sea exchange and its impact on biogeochemistry in the Indian Ocean 15. Microbial ecology of the Indian Ocean 16. Physical and biogeochemical characteristics of the Indian Ocean marginal seas 17. The Indian Ocean Observing System (IndOOS) 18. Modeling the Indian Ocean 19. Paleoclimate evidence of Indian Ocean variability across a range of timescales 20. Future projections for the tropical Indian Ocean