Ocean Carbon Storage across the middle Miocene: a new interpretation for the Monterey Event

• Published in: Nature communications Vol. 11; no. 1; pp. 134 - 11
• Main Authors: Sosdian, S M, Babila, T L, Greenop, R, Foster, G L, Lear, C H
• Format: Journal Article
• Language: English
• Published: England Nature Publishing Group 09.01.2020; Nature Publishing Group UK; Nature Portfolio
• Subjects: Calcium; Carbon; Carbon dioxide; Carbon isotopes; Carbon sequestration; Climate change; Continental shelves; Degassing; Dissolved inorganic carbon; Glaciation; Glaciology; Global cooling; Global warming; Hypotheses; Miocene; Negative feedback; Oceans; Organic carbon; Organic chemistry; Sea level rise; Temperature
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-019-13792-0

The Miocene Climatic Optimum (MCO, 14-17 Ma) was ~3-4 °C warmer than present, similar to estimates for 2100. Coincident with the MCO is the Monterey positive carbon isotope (δ C) excursion, with oceans more depleted in C relative to C 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 CO as a cause for the subsequent Miocene Climate Transition and Antarctic glaciation. However, this hypothesis cannot explain the multi-Myr lag between the δ C excursion and global cooling. We use planktic foraminiferal B/Ca, δ B, δ C, 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.