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Past and Future Extremes of the Indian Ocean

Kaustubh Thirumalai, Department of Earth, Environmental, and Planetary Sciences, Brown University
Fri, March 09, 2018, 10:30am - 11:30am

Video Broadcast

Host: Pedro Di Nezio

Climate variability in the Indian Ocean exerts a strong influence on the densely populated countries around its rim. Widespread droughts, wildfires, and flooding have been attributed to ocean-atmosphere dynamics in the Indian Ocean. One such event occurred during the devastating heat extreme of 2016 over Southeast Asia that caused extensive socioeconomic disarray. I will show how climate variability driven by the El Niño/Southern Oscillation (ENSO) and modulated by the Indian Ocean proved to be a causal factor for the 2016 heat event, and how global warming worsened the impact of this extreme. Apart from exacerbating ENSO-driven impacts, increasing levels of greenhouse gases are also expected to fundamentally alter the mean climate of the Indian Ocean. Pronounced changes in the background climate could lead to stronger climate variability in the Indian Ocean; however, model projections remain highly uncertain. I will present new proxy measurements and model simulations to investigate Indian Ocean climate variability during the Last Glacial Maximum (LGM), a period when background changes followed a pattern similar to that expected from greenhouse warming. The δ18O analysis of individual foraminiferal shells reveal immense increases in sea-surface temperature variability in the equatorial Indian Ocean, which we attribute to increased seasonality, but also to stronger and more frequent year-to-year warming and cooling events. These extremes are amplified by enhanced air-sea coupling induced by changes in background ocean conditions and demonstrate that the Indian Ocean can harbor even more intense extremes than those observed during modern history.