Indian monsoon variability over the past two millennia: From ocean to land

Project Overview

This project is motivated by two interconnected scientific debates, that is, (1) to what extent that the recent fast warming in the tropical Indian Ocean is driven by anthropogenic greenhouse forcing, and (2) whether the warming has dominated the decline of the Indian summer monsoon (ISM) over the Indian subcontinent in the past half-century. The two questions remain unsolved in part because very few sea surface temperature (SST) records are available from the central tropical Indian Ocean that extends beyond instrumental data, and very few highly resolved rainfall proxy records are available from ISM core region that have sufficient accuracy in chronological control. We hereby propose to develop two paleoclimate records from the region that can cover a substantial portion of the past two millennia with a seasonal-to-annual resolution or higher. They include a record of tropical Indian Ocean SST derived from trace metal ratios (Sr/Ca) in corals from the southern Maldives, and a record of ISM rainfall attained from oxygen stable isotope ratios (δ18O) in speleothems from Yunnan, southwestern China. By comparing the two records with other well-calibrated datasets from the region, we plan to help answer the aforementioned questions and shed light on the contributions of anthropogenic forcing to the long-term warming of the Indian Ocean and ISM activity.