Productivity feedback did not terminate the Paleocene-Eocene Thermal Maximum (PETM)
- 1Lamont-Doherty Earth Observatory, Columbia University, 61 Rt. 9W, Palisades, NY 10964-1000, USA
- 2Department of Earth and Environmental Sciences, Columbia University, NY 10027, USA
- 3Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge, CB2 3EQ, UK
- *now at: Department of Earth and Space Sciences and Institute of Geophysics and Planetary Physics, University of California, Los Angeles, 595 Charles Young Drive East, Los Angeles, CA 90095-1567, USA
Abstract. The Paleocene-Eocene Thermal Maximum (PETM) occurred approximately 55 million years ago, and is one of the most dramatic abrupt global warming events in the geological record. This warming was triggered by the sudden release of thousands of gigatons of carbon into the atmosphere and is widely perceived to be the best analogue for current anthropogenic climate change. Yet, the mechanism of recovery from this event remains controversial. A massive increase in the intensity of the marine biological pump ("productivity feedback") has been suggested to cause a drawdown of atmospheric CO2 and subsequent carbon sequestration in the ocean. A re-evaluation of the "productivity feedback hypothesis", based on biogenic barium mass accumulation rates (Ba-MARs) for a site in the Southern Ocean, finds that any increase in export production lagged the initial carbon release by at least ~70 000 years. This implies that export production did not facilitate rapid removal of excess carbon from the atmosphere. Thus, the most likely mechanism for carbon removal appears to be silicate weathering, which occurred at much slower rates than previously assumed.