Sexton, Philip F.; Norris, Richard D.; Wilson, Paul A.; Pälike, Heiko; Westerhold, Thomas; Röhl, Ursula; Bolton, Clara T. and Gibbs, Samantha
Eocene global warming events driven by ventilation of oceanic dissolved organic carbon.
Nature, 471 pp. 349–352.
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‘Hyperthermals’ are intervals of rapid, pronounced global warming known from six episodes within the Palaeocene and Eocene epochs (~65–34 million years (Myr) ago). The most extreme hyperthermal was the ~170 thousand year (kyr) interval2 of 5–7 °C global warming 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, and other, comparatively modest, hyperthermals have also been linked to the release of sedimentary. 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 shorter durations (~40 kyr) and more rapid recovery phases than the PETM. These findings point to the operation of fundamentally different forcing and feedback mechanisms than for the PETM, involving redistribution of carbon among Earth’s readily exchangeable surface reservoirs rather than carbon exhumation from, and subsequent burial back into, the sedimentary reservoir. Specifically, we interpret our records to indicate repeated, large-scale releases of dissolved organic carbon (at least 1,600 gigatonnes) from the ocean by ventilation (strengthened oxidation) of the ocean interior. The rapid recovery of the carbon cycle following each Eocene hyperthermal strongly suggests that carbon was re-sequestered by the ocean, rather than the much slower process of silicate rock weathering proposed for the PETM1. Our findings suggest that these pronounced climate warming events were driven not by repeated releases of carbon from buried sedimentary sources, but, rather, by patterns of surficial carbon redistribution familiar from younger intervals of Earth history.
||2011 Macmillan Publishers Limited
||climate science; geology and geophysics; earth science; palaeontology
||Science > Environment, Earth and Ecosystems
||22 Mar 2011 10:20
||24 Nov 2012 21:41
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Eocene global warming events driven by ventilation of oceanic dissolved organic carbon. (deposited 22 Mar 2011 10:20)
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