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G10 July 3 · 11:25–11:40 · Room 773 (7F)

Intensified Lacustrine Nitrous Oxide Emissions Linked to Global Climate Warming During the Toarcian Oceanic Anoxic Event

G10 Novel Isotope and Elemental Geochemical Proxies for Phanerozoic Stratigraphy and Ocean Chemistry Reconstructions 📅 Add to Calendar

Yuzhu Ge, Zhong Han, Benjamin T. Uveges, Hugh C. Jenkyns, David B. Kemp, Ying Cui, Tian Yang, Shaomin Zhang, Hanqin Tian, Xiumian Hu

Lacustrine nitrous oxide (N2O) is an important greenhouse gas that contributes to modern climate warming, but its role in past hyperthermal events is poorly understood. Here we report intensified N2O emission from the Sichuan megalake (>230,000 km2) during the Early Jurassic Toarcian Oceanic Anoxic Event, an event associated with protracted climate warming and environmental perturbations. Sedimentary strata deposited in the megalake during the T-OAE record a positive δ15Nbulk excursion, indicative of enhanced denitrification. This denitrification was coincident with a globally recognized negative carbon-isotope excursion (NCIE), increased organic matter deposition, element drawdown and deoxygenation in the megalake. The Sichuan megalake was large (covering ~10% of the present-day global lake surface area), and the interplay of enhanced lacustrine denitrification, deoxygenation, and Cu limitation likely promoted massive N2O emissions (conservatively estimated to be ~0.9 to 1.8 Gt) in the megalake alone. Our findings suggest that N2O emissions from expanded lacustrine systems were significant enough to weaken the climate effect of CO2drawdown through organic-matter burial. This process may have helped sustain global warming during past hyperthermal events.

lacustrine nitrogen oxideshyperthermal eventsdenitrificationcopper limitation
Affiliations
  1. State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation & Institute of
  2. Sedimentary Geology, Chengdu University of Technology, Chengdu 610059, China
  3. State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and
  4. Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China
  5. Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY, USA 14853
  6. Department of Earth Sciences, University of Oxford, South Parks Road, Oxford OX1 3AN, UK
  7. State Key Laboratory for Geomicrobiology and Environmental Changes and Hubei Key
  8. Laboratory for Critical Zone Evolution, School of Earth Sciences, China University of
  9. Geoscience, Wuhan 430074, China
  10. Department of Earth and Environmental Studies, Montclair State University, Montclair, NJ
  11. USA 07043
  12. Southwest Oil and Gas Company, SINOPEC, Chengdu 610041, China
  13. Department of Earth and Environmental Sciences, Boston College, Chestnut Hill, MA USA
  14. 02467
  15. State Key Laboratory of Critical Earth Material Cycling and Mineral Deposits, School of Earth
  16. Sciences and Engineering, Nanjing University, Nanjing 210023, China