Collaborative Research: P2C2--The Changing Width of the Tropics in Past, Present and Future Climate

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The research centers on the hypothesis that extreme warming, such as during the Early Eocene and under potential unmitigated climate scenarios, drives a substantial expansion of the tropical belt accompanied by poleward shifts in other aspects of the atmospheric circulation and large-scale hydroclimate. This interdisciplinary research integrates paleo-proxy data with climate modeling to investigate the changing width of the tropics during Late Paleocene and Early Eocene. The observational component of the research aims to provide a comprehensive Paleocene-Eocene hydrological data synthesis and data for a model-data comparison. The modelling component will analyze pre-existing coupled DeepMIP climate simulations of Paleocene-Eocene, conduct targeted atmosphere-only simulations to explore the sensitivity of the results to sea surface temperatures, and perform the data-model comparison.The poleward edge of the tropical Hadley cell is a fundamental characteristic of Earth’s climate. The edge of the Hadley cell marks the boundary between the tropics and extratropics - the Earth’s two main climate zones at the most basic level. Observations reveal a poleward expansion of the Hadley cell in recent decades, driving an expansion of the tropical belt with potentially significant implications for worldwide climate. The expansion has the potential to shift rain belts and cyclone tracks, expand deserts, and exacerbate droughts and wildfires. Climate models simulate the tropical expansion, albeit at lower rates than what is observed. This raises important questions about the causes behind the expansion and the ability of models to simulate the expansion as well as questions surrounding the magnitude of the widening under future global warming.The potential Broader Impacts include involving graduate and undergraduate students will be involved in the project, a plan for improving diversity and inclusion through existing programs, and a creative visual science journalism film project. Specifically, the diversity activities include collaboration with the Women in Science, Engineering and Mathematics Program (WISEM) by contributing hands-on activity modules for their annual outreach programs, participation in the Girls Lead the Way program for high school students, and also providing science experiment modules for Mines Girl Scout Engineering Day which welcomes 100 Junior Girl Scouts to participate in STEM activities.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.