Tropical hydroclimate change during the last deglaciation: a synthesis of isotope-enabled transient climate model simulations and proxy data

The tropics have profound influence on the global climate system, but the region’s response to changing climate remains unclear and the predictions of tropical precipitation and water cycling remain highly uncertain. This project aims to improve the ability of future climate projections in this region by using numerical model simulation and proxy derived records of water tracers of tropical hydroclimate to identify pan-tropical and regional responses to climate drivers under different boundary conditions. The investigation will focus on the last deglaciation period which is characterized by large shifts in atmospheric greenhouse gases concentrations, seasonal insolation, ice sheets, and sea level. Thus, the configuration of the last deglaciation creates a unique opportunity to study the tropical hydroclimate changes under different boundary condition than today. The overarching goal of this project is to gain new insight into the large-scale dynamics and controls on tropical hydroclimate through (1) syntheses of tropical water isotope records to characterize the spatiotemporal changes of tropical isotope hydrological records during the last deglaciation, and (2) testing critical hypotheses about the impact of external forcings and internal feedbacks on tropical rainfall. To accomplish this goal, the researchers propose a comprehensive pan-tropical data model comparison through integrating water-isotope based proxy-data, proxy system models, and new simulations with a state of-the-art isotope enabled transient climate model (iTRACE). Further, the researchers will perform new sensitivity experiments under different boundary conditions with isotope-enabled Community Earth System Model to test the influence of land-ocean configuration on orbital and millennial-scale variability across the tropics. The potential Broader Impacts include a better understanding of the spatiotemporal changes and regional drivers of tropical hydroclimate during the last deglaciation. The proposed research will assess the influence of precipitation amount relative to atmospheric circulation changes on precipitation thus potentially enhancing the interpretation of regional paleoclimate records. The project will support the professional development of an early career scientist at Brown University and the education and research training of undergraduate students from minority-serving-institutions through the Leadership Alliance-NSF-REU partnership at Brown University. Additionally, the researchers will develop a new seminar course on climate data analysis and data-model comparison for undergraduate and graduate students. 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.