Reconstructing the variability in the Indian monsoon over the last 20,000 years

The Asian monsoon rains provide freshwater to one of the most densely populated regions on Earth. However, despite the societal and economic importance of the monsoon system, its forcing mechanisms are not fully understood. It is widely accepted that on orbital timescales the strength of the Asian monsoon varies in response to changes in northern hemisphere (NH) summer insolation, which is primarily controlled by precession. Paleoclimate archives from around the region yield conflicting evidence about the timing of the monsoonal response with respect to NH insolation changes [e.g., Clemens and Prell, 2003; Wang et al., 2001], perhaps suggesting a complex relationship between insolation forcing and climatic response. We present new down-core records of paired planktic foraminiferal Mg/Ca-derived sea surface temperatures and seawater δ¹⁸O since the Last Glacial Maximum, which we generated using an intermediate depth sediment core retrieved from the Mahanadi Basin within the northwestern Bay of Bengal. When compared to previously published results [Rashid et al., 2007, 2011], our new results reveal geographic variations in sea surface hydrography within the Bay of Bengal over the past 20,000 years. The timing of these variations will be interpreted in light of known changes in NH summer insolation and within the context of previously published paleoclimate archives from the entire Asian monsoon region.