What caused the long duration of the Paleocene-Eocene Thermal Maximum?
Article first published online: 14 AUG 2013
©2013. American Geophysical Union. All Rights Reserved.
Volume 28, Issue 3, pages 440–452, September 2013
How to Cite
2013), What caused the long duration of the Paleocene-Eocene Thermal Maximum?, Paleoceanography, 28, 440–452, doi:10.1002/palo.20039.(
- Issue published online: 11 OCT 2013
- Article first published online: 14 AUG 2013
- Accepted manuscript online: 1 JUL 2013 11:46AM EST
- Manuscript Accepted: 28 JUN 2013
- Manuscript Revised: 27 JUN 2013
- Manuscript Received: 16 APR 2013
Paleorecords show that the Paleocene-Eocene Thermal Maximum (PETM, ∼56 Ma) was associated with a large carbon cycle anomaly and global warming >5 K, which persisted for at least 50 kyr. Conventional carbon cycle/climate models that include a single initial carbon input pulse over ∼10 kyr fail to reproduce the long duration of the PETM without invoking additional, slow carbon release over more than 50 kyr (hereafter referred to as bleeding). However, a potential carbon source for the bleeding, as well as its release mechanism, has hitherto remained elusive. Here I present first-principle calculations of heat transfer in marine sediments which demonstrate that a bottom water temperature anomaly as generated during the PETM takes tens of thousands of years to penetrate the top few hundred meters of deep-sea sediments. While the initial temperature rise has been suggested to cause dissociation of the majority of oceanic methane hydrate within ∼10 kyr, my calculations reveal a long tail of hydrate dissociation, causing smaller but continued carbon release substantially beyond 10 kyr. In addition, I suggest that temperature-enhanced metabolic processes in marine sediments and the absence of methane hydrate deposition during the PETM contributed to prolonged carbon input during the event. Enhanced fluxes of methane over this time scale would have sustained the carbon isotope excursion and amplified long-term greenhouse warming by elevating atmospheric concentrations of steady state CH4, or in oxidized form, CO2.