Eocene global warming events driven by ventilation of oceanic dissolved organic carbon

• Published in: Nature (London) 2011-03, Vol.471 (7338), p.349-352
• Main Authors: Sexton, Philip F., Norris, Richard D., Wilson, Paul A., Pälike, Heiko, Westerhold, Thomas, Röhl, Ursula, Bolton, Clara T., Gibbs, Samantha
• Format: Article
• Language: English
• Subjects: 704/106/413; 704/2151/2738; Atlantic Ocean; Atmosphere - chemistry; Atmospheric carbon dioxide; Carbon; Carbon Cycle; Climate change; Dissolved organic carbon; Earth orbits; Earth sciences; Earth, ocean, space; Environmental aspects; Environmental Sciences; Eocene; Exact sciences and technology; Foraminifera - metabolism; Geologic Sediments - chemistry; Global Changes; Global warming; Global Warming - history; Greenhouse gases; History, Ancient; Humanities and Social Sciences; letter; Marine geology; multidisciplinary; Oceans and Seas; Paleocene; Plankton; Reservoirs; Science; Science (multidisciplinary); Seawater - chemistry; Stratigraphy; Temperature; Ventilation
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/nature09826

Carbon release and global warming One of the most remarkable global warming events or 'hyperthermals' in Earth's past was the Palaeocene–Eocene thermal maximum (PETM). This occurred about 56 million years ago, probably as a result of the release of methane from sediments. Several other, less-severe warming periods occurred around 6 million to 8 million years after the PETM. Sexton et al . show that these smaller events were brief and surprisingly frequent, following a tempo set by Earth's orbit. Their rapid onset and recovery suggests a mechanism that was mainly dependent on shuffling carbon between the atmosphere and a dissolved, organic form in the ocean, in sharp contrast to the more sluggish greenhouse-gas release from buried carbon reservoirs during the PETM. These findings could help to address fundamental questions about how the global carbon cycle operates during extreme warming events. One of the most remarkable global warming events in the history of the Earth was the Palaeocene–Eocene Thermal Maximum (PETM), 56 million years ago, which is thought to have been caused by the release of greenhouse gases from mineral weathering. Several other, less severe warming periods occurred around 6–8 million years after the PETM. This paper shows that these smaller events were brief and surprisingly frequent, to a tempo paced by the Earth's orbit. Their rapid onset and recovery indicates a mechanism primarily dependent on shuffling carbon between the atmosphere and a dissolved, organic form in the ocean, in sharp contrast to the PETM's more sluggish greenhouse gas release from buried carbon reservoirs. ‘Hyperthermals’ are intervals of rapid, pronounced global warming known from six episodes within the Palaeocene and Eocene epochs (∼65–34 million years (Myr) ago) 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 . The most extreme hyperthermal was the ∼170 thousand year (kyr) interval 2 of 5–7 °C global warming 3 during the Palaeocene–Eocene Thermal Maximum (PETM, 56 Myr ago). The PETM is widely attributed to massive release of greenhouse gases from buried sedimentary carbon reservoirs 1 , 3 , 6 , 11 , 14 , 15 , 16 , 17 , and other, comparatively modest, hyperthermals have also been linked to the release of sedimentary carbon 3 , 6 , 11 , 16 , 17 . Here we show, using new 2.4-Myr-long Eocene deep ocean records, that the comparatively modest hyperthermals are much more numerous than previously documented, paced by the eccentricity of Earth’s orbit and have