Orbital forcing of the Paleocene and Eocene carbon cycle

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doi: 10.1002/2016PA003054
Author(s): Zeebe, Richard E.; Westerhold, Thomas; Littler, Kate; Zachos, James C.
Author Affiliation(s): Primary:
University of Hawai'i at Manoa, School of Ocean and Earth Science and Technology, Honolulu, HI, United States
University of Bremen, Germany
University of Exeter, United Kingdom
University of California at Santa Cruz, United States
Volume Title: Paleoceanography
Source: Paleoceanography, 32(5), p.440-465. Publisher: American Geophysical Union, Washington, DC, United States. ISSN: 0883-8305 CODEN: POCGEP
Note: In English. NSF grants OCE-1220615 and OCE-1658023; includes 2 appendices. 80 refs.; illus.
Summary: Multimillion-year proxy records across the Paleocene and Eocene show prominent variations on orbital time scales. The cycles, which have been identified at various sites across the globe, preferentially concentrate spectral power at eccentricity and precessional frequencies. It is evident that these cycles are an expression of changes in global climate and carbon cycling paced by astronomical forcing. However, little is currently known about the link between orbital forcing and the carbon cycle-climate system and the amplitude of associated atmospheric CO2 variations. Here we use simple and complex carbon cycle models to explore the basic effect of different orbital forcing schemes and noise on the carbon cycle. Our primary modeling target is the high-resolution, ∼7.7 Myr long, benthic isotope record at Ocean Drilling Program Site 1262 in the South Atlantic. For direct insolation forcing (as opposed to artificial eccentricity-tilt-precession), one major challenge is understanding how the system transfers spectral power from high to low frequencies. We discuss feasible solutions, including insolation transformations analogous to electronic AC-DC conversion (DC'ing). Regarding mechanisms, we focus on tropical insolation and a long-term carbon imbalance in terrestrial organic burial/oxidation but do not rule out other scenarios. Our analysis shows that high-latitude mechanisms are unlikely drivers of orbitally paced changes in the late Paleocene-early Eocene (LPEE) Earth system. Furthermore, we provide constraints on the origin and isotopic composition of a possible LPEE cyclic carbon imbalance/source responding to astronomical forcing. Our simulations also reveal a mechanism for the large δ13C-eccentricity lag at the 400 kyr period observed in Paleocene, Oligocene, and Miocene sections. We present the first estimates of orbital-scale variations in atmospheric CO2 during the late Paleocene and early Eocene. Abstract Copyright (2017), . American Geophysical Union. All Rights Reserved.
Year of Publication: 2017
Research Program: ODP Ocean Drilling Program
Key Words: 02 Geochemistry; 12 Stratigraphy, Historical Geology and Paleoecology; Amplitude; Atlantic Ocean; C-13/C-12; Carbon; Carbon cycle; Cenozoic; Climate forcing; Eccentricity; Elastic waves; Eocene; Geochemical cycle; Insolation; Isotope ratios; Isotopes; LOSCAR; Leg 208; Milankovitch theory; Mineralization; Numerical models; O-18/O-16; ODP Site 1262; Obliquity of the ecliptic; Ocean Drilling Program; Orbital forcing; Organic compounds; Oxygen; Paleocene; Paleogene; South Atlantic; Stable isotopes; Statistical analysis; Tertiary; Time series analysis; Walvis Ridge
Coordinates: S271100 S271100 E0013500 E0013400
Record ID: 2017060832
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from John Wiley & Sons, Chichester, United Kingdom