The Paleocene-Eocene Thermal Maximum: How much carbon is enough?

• Published in: Paleoceanography
• Main Authors: Meissner, KJ, Bralower, TJ, Alexander, K, Jones, TD, Sijp, W, Ward, M
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: American Geophysical Union (AGU) 2014
• Subjects: 13 Climate Action; anzsrc-for: 0402 Geochemistry; anzsrc-for: 0405 Oceanography; anzsrc-for: 0602 Ecology; Arctic; North Atlantic
• Online Access: http://hdl.handle.net/1959.4/unsworks_13608; https://doi.org/10.1002/2014PA002650

The Paleocene-Eocene Thermal Maximum (PETM),55.53 million years before present, was an abrupt warming event that involved profound changes in the carbon cycle and led to major perturbations of marine and terrestrial ecosystems. The PETM was triggered by the release of a massive amount of carbon, and thus, the event provides an analog for future climate and environmental changes given the current anthropogenic CO 2 emissions. Previous attempts to constrain the amount of carbon released have produced widely diverging results, between 2000 and 10,000 gigatons carbon (GtC). Here we use the UVic Earth System Climate Model in conjunction with a recently published compilation of PETM temperatures to constrain the initial atmospheric CO 2 concentration as well as the total mass of carbon released during the event. Thirty-six simulations were initialized with varying ocean alkalinity, river runoff, and ocean sediment cover. Simulating various combinations of pre-PETM CO 2 levels (840, 1680, and 2520 ppm) and total carbon releases (3000, 4500, 7000, and 10,000 GtC), we find that both the 840 ppm plus 7000 GtC and 1680 ppm plus 7000-10,000 GtC scenarios agree best with temperature reconstructions. Bottom waters outside the Arctic and North Atlantic Oceans remain well oxygenated in all of our simulations. While the recovery time and rates are highly dependent on ocean alkalinity and sediment cover, the maximum temperature anomaly, used here to constrain the amount of carbon released, is less dependent on this slow-acting feedback. Key PointsWe constrain pre-PETM CO 2 concentration and total amount of carbon releasedData-model comparison with full OGCM including long-term transient simulationsOnly carbon-intensive scenarios are compatible with data