Carbon Sources and Sinks Over the Last 750 Million Years and Relationships to Greenhouse and Icehouse Climates
Abstract
Over geological timescales, Earth's atmospheric CO2 concentration is determined by a complex interplay of carbon sources and sinks. The apparent response of many carbon sinks to changes in surface temperature and CO2 concentration implies negative feedback and ultimately stabilization of climate, but enhancements of sink processes, and/or changes to the volcanic CO2 source may result in significant shifts in stable CO2 concentration and surface temperature. Observed `icehouse' climate states are traditionally linked to enhancements of carbon sinks due to tectonic or biologically-driven changes to continental weathering and/or organic carbon burial. But recent work shows a qualitative relationship between the extent of arc volcanism and global temperature (McKenzie et al., 2016), shifting the focus to CO2 sources, and implying a diminished role for sink processes. Here we integrate a new quantitative measure of arc degassing rates with current approximations for changes in carbon sink processes in a global biogeochemical model for the last 750Myrs, and compare the results to a suite of geochemical data and to long term global temperature proxies. We investigate whether currently-proposed CO2-regulation mechanisms appear reasonable, and identify the likely key processes influencing climate stability during different periods of Earth history. References:McKenzie, N. R., Horton, B. K., Loomis, S. E., Stockli, D. F., Planavsky, N. J. & Cin-Ty, A. L. Continental arc volcanism as the principal driver of icehouse-greenhouse variability. Science 352, 444-447 (2016).
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFMPP22B..06M
- Keywords:
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- 0325 Evolution of the atmosphere;
- ATMOSPHERIC COMPOSITION AND STRUCTUREDE: 0428 Carbon cycling;
- BIOGEOSCIENCESDE: 1030 Geochemical cycles;
- GEOCHEMISTRYDE: 5220 Hydrothermal systems and weathering on other planets;
- PLANETARY SCIENCES: ASTROBIOLOGY