资源环境科技发展态势分析平台

The Miocene Climatic Optimum (MCO, 14-17 Ma) was similar to 3-4 degrees C warmer than present, similar to estimates for 2100. Coincident with the MCO is the Monterey positive carbon isotope (delta C-13) excursion, with oceans more depleted in C-12 relative to C-13 than any time in the past 50 Myrs. The long-standing Monterey Hypothesis uses this excursion to invoke massive marine organic carbon burial and draw-down of atmospheric CO2 as a cause for the subsequent Miocene Climate Transition and Antarctic glaciation. However, this hypothesis cannot explain the multi-Myr lag between the delta C-13 excursion and global cooling. We use planktic foraminiferal B/Ca, delta B-11, delta C-13, and Mg/Ca to reconstruct surface ocean carbonate chemistry and temperature. We propose that the MCO was associated with elevated oceanic dissolved inorganic carbon caused by volcanic degassing, global warming, and sea-level rise. A key negative feedback of this warm climate was the organic carbon burial on drowned continental shelves.