Collaborative Research: P2C2--Expansion/Contraction of the Intertropical Convergence Zone; An Emerging Mechanism of Tropical Precipitation Changes for Reinterpreting Paleoclimate

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The spatial distribution of tropical precipitation is determined by the average location and seasonal march of the intertropical convergence zone (ITCZ). The latitudinal shift of the ITCZ is typically employed as the go-to theory for interpreting past hydroclimate changes and defining mechanisms of the response to climate forcing (past and future). This project, however, is based on the premise that the simultaneous contraction and intensification (CI) of the ITCZ is a far more powerful mode of tropical precipitation changes (by a factor of 4) in response to both paleoclimate and anthropogenic forcing than the more commonly employed ITCZ shift.The overarching goal of the project is to couple reconstructions of past changes in the CI mode from paleoclimate proxy records with a dynamical framework of the CI mode to constrain future tropical precipitation changes and variability. This specific aims are to: i) explore the dynamics of the CI mode to identify the mechanisms that lead to the direction of changes seen in simulations of past and future climate as well as evaluate the uncertainties in these processes and ii) use the emerging knowledge of the CI mode to reinterpret the paleoclimate record to constrain the past behavior of ITCZ shifts versus CI. The project would help develop a deeper understanding of the ITCZ and potentially improve the ability of climate models to forecast broad-scale future changes (and variability) in the magnitude and spatial structure topical precipitation. The project would also support two early career scientists and leverage existing public outreach programs in science at the University of Washington and the University of California-Berkeley.