Earth System Model Analysis of How Astronomical Forcing Is Imprinted Onto the Marine Geological Record: The Role of the Inorganic (Carbonate) Carbon Cycle and Feedbacks

P. Vervoort*, S. Kirtland Turner, F. Rochholz, A. Ridgwell

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

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Abstract

Astronomical cycles are strongly expressed in marine geological records, providing important insights into Earth system dynamics and an invaluable means of constructing age models. However, how various astronomical periods are filtered by the Earth system and the mechanisms by which carbon reservoirs and climate components respond, particularly in absence of dynamic ice sheets, is unclear. Using an Earth system model that includes feedbacks between climate, ocean circulation, and inorganic (carbonate) carbon cycling relevant to geological timescales, we systematically explore the impact of astronomically‐modulated insolation forcing and its expression in model variables most comparable to key paleoceanographic proxies (temperature, the δ13C of inorganic carbon, and sedimentary carbonate content). Temperature predominately responds to obliquity and is little influenced by the modeled carbon cycle feedbacks. In contrast, the cycling of nutrients and carbon in the ocean generates significant precession power in atmospheric CO2, benthic ocean δ13C, and sedimentary wt% CaCO3, while inclusion of marine sedimentary and weathering processes shifts power to the long eccentricity period. Our simulations produce reduced pCO2 and dissolved inorganic carbon δ13C at long eccentricity maxima and, contrary to early Cenozoic marine records, CaCO3 preservation in the model is enhanced during eccentricity modulated warmth. Additionally, the magnitude of δ13C variability simulated in our model underestimates marine proxy records. These model‐data discrepancies hint at the possibility that the Paleogene silicate weathering feedback was weaker than modeled here and that additional organic carbon cycle feedbacks are necessary to explain the full response of the Earth system to astronomical forcing.
Original languageEnglish
Article numbere2023PA004826
Number of pages20
JournalPaleoceanography and Paleoclimatology
Volume39
Issue number3
Early online date4 Mar 2024
DOIs
Publication statusPublished - 4 Mar 2024

Bibliographical note

We thank Michel Crucifix and his research team for identifying the error in the original insolation code that led us to re-run the simulations and resubmit this manuscript with the corrected results.

Keywords

  • astronomical forcing
  • carbon cycle
  • feedbacks
  • greenhouse climate
  • earth system modeling
  • time series analysis

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