Phanerozoic Chemical Weathering, CO2 Budgets and Global Climate

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Models of the long-term, global carbon cycle have lacked a geographic dimension; model input and output have been restricted to global-mean values. Climate change on million-year time scales can be driven by redistribution of the continents and their weathering lithologies (as this affects atmospheric pCO2). This project will explore the nature of Phanerozoic climate change by performing several new climate simulations. Runs at different pCO2's for the same time periods will elucidate the relationship between global temperature and runoff (the two most important variables affecting chemical weathering rates and thus pCO2). These climate variables will then be used in calculations of global weathering rates, using paleogeologic maps prepared during our previous research. In addition, two other important factors, topography (relief) and biological enhancement of chemical weathering rates, will be assessed, using present-day observations of their affect on soil and stream chemistry, and by assembling and reconstructing paleophytogeographies. The goal of this research is to create a realistic, coupled model of climate and biogeochemical cycles that can be used to investigate the geographic and temporal variability of Phanerozoic climate.