Using biomarkers to explore the Earth System
On very long timescales, the Earth's climate is regulated by a range of predominantly negative feedback processes. However, on shorter timescales, from hundreds to tens of thousands of years, the organic component of the carbon cycle is critical, and both positive and negative carbon cycle feedbacks occur. These are vital to understanding past climatic events but also our future. Popular science discourse is now laden with references to tipping points, feedbacks and runaway greenhouses. methane bombs and clathrate guns. These processes can be interrogated in modern and ancient contexts with both top-down or bottom-up approaches, by either examining the global (typically carbon isotopic) fingerprint of OM release/burial or deciphering the underlying mechanisms that govern OM preservation or oxidation. I'll try to explore both, but don't expect straight-forward answers! It's complicated! I will draw on lessons learned by studying many of the carbon cycle perturbations of the Phanerozoic and especially the Palaeocene-Eocene Thermal Maximum, but also the characterisation and reactivity of OM in various settings, especially in terrestrial contexts where the controls on organic matter preservation are particularly complicated. Not unusually, I will probably raise more questions than I answer.