P2C2: Synthesis Study of the Tropical Rain Belt Through the Holocene

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This project is motivated by the idea that the tropical rain belt (TRB), including the oceanic and continental Inter-tropical Convergence Zone (ITCZ) and seasonal monsoon systems, plays a fundamental role in the Earth's climate and strongly impacts societies, ecosystems, and global climate. During the Holocene, forced changes in the TRB have been invoked to explain many observed failures and increases in tropical rainfall. However, the physical processes driving changes in TRB dynamics and their relationship to climate forcings remain unclear.This award generally aims to evaluate the drivers of Holocene TRB variations by utilizing a wide network of tropical paleo-hydroclimate records and new isotope-enabled model simulations. This project aims to: (1) evaluate the response of the TRB's distinct components (convergence over ocean and land, and seasonal monsoons) to Holocene climate forcing functions and feedbacks, including biogeophysical feedbacks and interactions with ENSO; and (2) translate changes in the TRB into changes in proxy recorders, including those based on precipitation isotope ratios.The scientific objectives of this project will be achieved through a synthesis of climate proxy records of TRB position and intensity and a series of model experiments with NCAR's isotope-enabled Community Earth System Model (CESM). Time slices at different stages of the Holocene will provide a climate dynamical context for the synthesized data product. A set of sensitivity experiments will help determine the degree to which biosphere-atmosphere feedbacks and ENSO/TRB (El Nino-Southern Oscillation) interactions influence both isotopic and non-isotopic proxies. A toolkit of emerging proxy system models will be integrated into CESM to compare directly with the network of proxy records. It is expected that this project will help evaluate the forced changes in the TRB projected for the 21st century.The Broader Impacts include upgrading and maintaining the isotopic version of the CESM, enabling the development of a post-doctoral scholar community at the institution, developing discovery-based undergraduate educational experiences, and adding new scientific data and analyses to help improve the understanding of natural climate variability.