Paleocene–Eocene Thermal Maximum

Paleocene–Eocene Thermal Maximum
Name	Paleocene–Eocene Thermal Maximum
Caption	Global distribution of PETM records
Start	56.0 Ma
End	55.5 Ma
Period	Paleogene
Major events	Carbon isotope excursion, deep-sea warming, biotic turnover

Paleocene–Eocene Thermal Maximum

The Paleocene–Eocene Thermal Maximum (PETM) was a geologically brief interval of extreme warmth near the Paleocene–Eocene boundary characterized by rapid carbon-cycle perturbation, global temperature rise, and widespread biotic change. It has been the focus of studies by researchers associated with institutions such as University of Oxford, United States Geological Survey, Lamont–Doherty Earth Observatory, Scripps Institution of Oceanography, and Max Planck Society and is recorded in marine and continental archives used by projects like the Ocean Drilling Program, Integrated Ocean Drilling Program, and International Continental Scientific Drilling Program.

Background and context

The event occurred near the transition between the Paleocene and the Eocene epochs and coincided with shifts in paleogeography reconstructed by proponents of plate reconstructions like Alfred Wegener and refined by models from groups at Cambridge University and Massachusetts Institute of Technology. It followed earlier Cenozoic greenhouse conditions and preceded cooling trends leading toward the Eocene–Oligocene extinction event and faunal changes documented in collections at the Natural History Museum, London and the Smithsonian Institution. Stratigraphic frameworks from the International Commission on Stratigraphy and magnetostratigraphy tied to results from researchers at University of California, Santa Cruz and ETH Zurich place the event within chron C24r.

Causes and carbon cycle perturbations

Hypotheses for the carbon injection invoke sources and processes studied by teams at NASA Goddard Institute for Space Studies, National Oceanic and Atmospheric Administration, National Aeronautics and Space Administration, and laboratories at Lamont–Doherty Earth Observatory: destabilization of methane hydrates on continental margins such as those explored near the Blake Nose and Wilkes Land; massive volcanism related to the North Atlantic Igneous Province and flood basalts tied to plate interactions documented by geologists at University of Oslo; permafrost thawing in regions like Siberia and Greenland; and release from kerogen oxidation in basins studied at British Geological Survey and Geological Survey of Canada. Geochemists at University of Texas at Austin and Caltech analyzed the negative carbon isotope excursion (CIE) recorded in carbonate and organic matter, integrating data frameworks from GEOSECS and isotope labs at ETH Zurich and University of Bremen.

Global climate and environmental impacts

Global sea-surface temperatures and deep-ocean temperatures rose substantially, inferred from proxies used by researchers at Woods Hole Oceanographic Institution and University of Southampton such as oxygen isotopes and Mg/Ca ratios collected on cores from the Atlantic Ocean, Pacific Ocean, Arctic Ocean, and Southern Ocean. Terrestrial climates shifted with enhanced hydrological cycling described in paleobotanical studies at Kew Gardens and palynological analyses from the Royal Botanic Gardens, Edinburgh. Sea-level responses, carbonate dissolution, and ocean acidification effects were investigated by scientists at University of Miami and Florida State University and linked to carbonate compensation feedbacks analyzed in work from Columbia University and Princeton University.

Biotic responses and extinction/turnover

Marine and terrestrial biotas experienced turnover: deep-sea benthic foraminifera extinctions catalogued by teams at Plymouth University and Vrije Universiteit Amsterdam contrast with radiation of planktonic foraminifera and calcareous nannoplankton studied at University of Leeds and University of Vienna. Mammalian faunal dispersals and dwarfing events across North America and Europe were described by paleontologists at Yale University, University of Michigan, University of California, Berkeley, and the American Museum of Natural History. Flora changes including leaf margin analyses were performed at University of Arizona and State University of New York at Stony Brook, while insect and freshwater records were assembled by researchers at University of Kansas and University of Arizona Natural History Collections.

Geological and geochemical evidence

Sedimentary archives from marine cores recovered by the Deep Sea Drilling Project and Ocean Drilling Program provide records of carbonate dissolution, clay mineralogy, and laminated sediments studied by geologists at Texas A&M University and University of Barcelona. Stable isotope excursions in δ13C and δ18O measured in laboratories at University of Bristol and University of New Hampshire are corroborated by trace element shifts analyzed at National Institute of Standards and Technology. Biomarker evidence including hopanes and GDGTs were interpreted by groups at University of Copenhagen and University of California, Davis to infer temperature and methanogenic contributions. Paleomagnetic constraints from institutes like Potsdam Institute for Climate Impact Research aided correlation with zonal biostratigraphy and magnetostratigraphy.

Chronology and duration

High-resolution age models developed using orbital tuning methods by teams at ETH Zurich, University of Bergen, and University of Edinburgh and radiometric constraints from Argon–argon dating at laboratories in Berkeley place the onset at about 56.0 million years ago with estimates of duration ranging from ~100 kyr to >200 kyr. Cyclostratigraphic approaches used by investigators at National Taiwan University and University of Bern and integration with magnetochron boundaries refined by the International Paleomagnetic Working Group constrain onset rates and recovery intervals.

Modeling and implications for future climate

Earth system models applied by groups at Met Office Hadley Centre, NOAA Geophysical Fluid Dynamics Laboratory, NCAR, Max Planck Institute for Meteorology, and Lawrence Berkeley National Laboratory simulate carbon release scenarios, feedbacks, and transient warming patterns that inform debates at forums like the Intergovernmental Panel on Climate Change. Comparisons between PETM carbon fluxes and modern anthropogenic emissions examined by researchers at Stanford University and Harvard University highlight differences in rate, magnitude, and biotic adaptability; these insights are used by policymakers and climate scientists connected to United Nations Environment Programme and national research programs to assess long-term climate sensitivity and tipping points.

Category:Paleocene Category:Eocene Category:Climate events