The role of pCO2 in astronomically-paced climate and carbon cycle variations in the middle Miocene

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http://abstractsearch.agu.org/meetings/2017/FM/PP33C-1346.html
Author(s): Penman, Donald E.; Hull, Pincelli M.; Scher, Howie; Kirtland Turner, Sandra; Ridgwell, Andy
Author Affiliation(s): Primary:
Yale University, Department of Geology and Geophysics, New Haven, CT, United States
Other:
University of South Carolina, United States
Scripps Institution of Oceanography, United States
University of Bristol, United Kingdom
Volume Title: AGU 2017 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2017; American Geophysical Union 2017 fall meeting, New Orleans, LA, Dec. 11-15, 2017. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: The pace of Earth's background climate variability is known to be driven by the Milankovitch cycles, variations in Earth's orbital parameters and axial tilt. While the Milankovitch (orbital) theory of climate change is very nearly universally accepted, the climate system mechanisms and feedbacks responsible for amplifying orbital cycles preserved in the geologic record remain uncertain. For the late Pleistocene, the ice core-derived record of atmospheric carbon dioxide (pCO2) is strongly coupled with global temperature on orbital time scales, indicating that internal feedbacks involving the carbon cycle amplify or even cause the large changes in global temperature during orbitally driven glacial-interglacial cycles. However, for earlier time periods beyond the range of ice cores (the last ≈800 kyr), it is not possible to directly compare records of pCO2 to orbital climate cycles because there are no high-resolution (orbitally resolved) records of pCO2 before the Pliocene. We address this deficiency with a high-resolution (≈5-10 kyr spacing) record of planktonic foraminiferal d11B-derived surface seawater pH (as well as d13C and trace metal analyses) over a 500 kyr time window in a sedimentary record with known Milankovitch-scale climate and carbon cycle oscillations: the Middle Miocene (14.0 - 14.5 Ma) at ODP Site 926 (subtropical North Atlantic). The resulting pH record can be used to constrain atmospheric pCO2, allowing comparison of the timescale and magnitude of carbon cycle changes during a period of eccentricity-dominated variability in the response of the global climate system (the Late Pleistocene) with a period of obliquity-dominance (the middle Miocene). These new records of planktic d11B and d13C will then be used to guide simulations of astronomical climate forcing in Earth System models, resulting in refined estimates of pCO2 changes over orbital cycles and providing quantitative constraints on the mechanisms and feedbacks responsible for the Milankovitch control of climate and carbon cycling.
Year of Publication: 2017
Research Program: ODP Ocean Drilling Program
Key Words: 02 Geochemistry; 12 Stratigraphy, Historical Geology and Paleoecology; Atlantic Ocean; Atmosphere; B-11/B-10; Boron; C-13/C-12; Carbon; Carbon cycle; Carbon dioxide; Ceara Rise; Cenozoic; Climate forcing; Equatorial Atlantic; Geochemical cycle; Isotope ratios; Isotopes; Leg 154; Middle Miocene; Milankovitch theory; Miocene; Neogene; North Atlantic; ODP Site 926; Ocean Drilling Program; Orbital forcing; Paleoclimatology; Stable isotopes; Tertiary
Coordinates: N034309 N034309 W0425430 W0425430
Record ID: 2018093775
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