Collaborative Research: P2C2--Reconstructing Atmospheric 14C across the Inter Tropical Convergence Zone Using Tropical Tree Rings from South America and Central Africa

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This project aims to develop an observational record of atmospheric radiocarbon (14C) data post-1950 by using calendrically dated tree rings across the intertropical convergence zone (ITCZ). The tree-ring sites are located in South America (Ecuador, Peru, Bolivia, Brazil) and central Africa (Cameroon) across the ITCZ band. These new 14C data will be used to constrain the spatial pattern of atmospheric 14C in the southern hemisphere, which currently relies on samples collected mostly in the eastern part of the southern hemisphere. The researchers will additionally measure the ring width and the stable isotope compositions of Oxygen and Carbon from the tree rings to investigate factors that can cause spatial and temporal variations of 14C variations. These include the seasonality of tree growth and the source of rainwater which reflects atmospheric circulation dynamics. The combined proxies aim to improve: 1) regional and local features of ITCZ circulation and inter-hemispheric exchange; 2) prediction of the ITCZ shifts in response to anthropogenic forcings; 3) the 14C calibration curve for the equatorial southern hemisphere.The potential Broader Impacts include a better definition of the intra-hemispheric 14C zonal division at lower latitudes, and the 14C timescale in Southern hemisphere which will benefit the paleoclimate community for chronology constraints (accuracy of the radiocarbon method) of the Holocene and climate dynamics of the ITCZ. Results of this project will benefit other fields including: radiocarbon calibration, astrophysics, ecology, biogeochemical and Earth science and archeology. The project will provide training for two undergraduate students and one PhD student. A radiocarbon short course will be organized at University of California Irvine where researchers, students and international collaborators will participate. The data of these project will be integrated in the International intercalibration curve of atmospheric radiocarbon.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.