Predicting trends in atmospheric CO2 across the Mid-Pleistocene Transition using existing climate archives

Full description

This dataset contains:
1) A prediction of atmospheric CO2 concentrations spanning 0 to 1.8 Million years ago (Mya), as published in:
Martin, J. R. W., Pedro, J., and Vance, T. R.: Predicting trends in atmospheric CO2 across the Mid-Pleistocene Transition using existing climate archives, EGUsphere [preprint], https://doi.org/10.5194/egusphere-2022-574, 2022.
2) An extended prediction of atmospheric CO2 spanning 1.8 to 5.3 Mya. This extended portion of the dataset is currently unpublished.
3) The model code (R Project) used for the reconstruction and in the data analysis.
The CO2 prediction is based on a generalised least squares (GLS) regression using the LR04 marine sediment core ẟ18Ocalcite stack (Lisiecki and Raymo, 2005) and existing Antarctic ice core CO2 data (Bereiter et al., 2015). Full description of methods in the paper.

Paper abstract:
During the Mid-Pleistocene Transition (MPT), ca. 1200–800 thousand years ago (kya), the Earth's glacial cycles changed from 41 kyr to 100 kyr periodicity. The emergence of this longer ice-age periodicity was accompanied by higher global ice volume in glacial periods and lower global ice volume in interglacial periods. Since there is no known change in external orbital forcing across the MPT, it is generally agreed that the cause of this transition is internal to the earth system. Resolving the climate, carbon cycle and cryosphere processes responsible for the MPT remains a major challenge in earth and palaeoclimate science. To address this challenge, the international ice core community has prioritised recovery of an ice core record spanning the MPT interval.
Here we present results from a simple generalised least squares (GLS) model that predicts atmospheric CO2 out to 1.8 Myr. Our prediction utilises existing records of atmospheric carbon dioxide (CO2) from Antarctic ice cores spanning the past 800 kyr along with the existing LR04 benthic delta 18Ocalcite stack (Lisiecki and Raymo, 2005; hereafter 'benthic delta 18O stack') from marine sediment cores. Our predictions assume that the relationship between CO2 and benthic delta 18O over the past 800 thousand years can be extended over the last one and a half million years. The implicit null hypothesis is that there has been no fundamental change in feedbacks between atmospheric CO2 and the climate parameters represented by benthic delta 18O, global ice volume and ocean temperature.
We test the GLS-model predicted CO2 concentrations against observed blue ice CO2 concentrations, delta 11B-based CO2 reconstructions from marine sediment cores and delta 13C of leaf-wax based CO2 reconstructions (Higgins et al., Yan et al., 2019 and Yamamoto et al., 2022). We show that there is not clear evidence from the existing blue ice or proxy CO2 data to reject our predictions nor our associated null-hypothesis. A definitive test and/or rejection of the null hypothesis may be provided following recovery and analysis of continuous oldest ice core records from Antarctica, which are still several years away. The record presented here should provide a useful comparison for the oldest ice core records and opportunity to provide further constraints on the processes involved in the MPT.

References
Bereiter, B., Eggleston, S., Schmitt, J., Nehrbass-Ahles, C., Stocker, T. F., Fischer, H., Kipfstuhl, S., and Chappellaz, J.: Revision of the EPICA Dome C CO2 record from 800 to 600 ky before present, Geophys. Res. Lett., 42, 542-549, https://doi.org/10.1002/2014gl061957, 2015.
Higgins, J. A., Kurbatov, A. V., Spaulding, N. E., Brook, E., Introne, D. S., Chimiak, L. M., Yan, Y., Mayewski, P. A., and Bender, M. L.: Atmospheric composition 1 million years ago from blue ice in the Allan Hills, Antarctica, P. Natl. Acad. Sci. USA., 112, 6887, https://doi.org/10.1073/pnas.1420232112, 2015.
Lisiecki, L. E. and Raymo, M. E.: A Pliocene-Pleistocene stack of 57 globally distributed benthic delta 18O records, Paleoceanography, 20, PA1003, https://doi.org/10.1029/2004pa001071, 2005.
Yamamoto, M., Clemens, S.C., Seki, O., Tsuchiya, Y., Huang, Y., O'ishi, R., and Abe-Ouchi, A.: Increased interglacial atmospheric CO2 levels followed the mid-Pleistocene Transition, Nat. Geosci., 15(4), 307–313, https://doi.org/10.1038/s41561-022-00918-1, 2022.
Yan, Y., Benderm M.l., Brook, E.J., Clifford, H.M., Kemeny, P.C., Kurbatov, A.V., Mackay, S., Mayewski, P.A., Ng, J., Severinghaus J.P., and Higgins, J.A.: Two-million-year-old snapshots of atmospheric gases from Antarctic ice, Nature, 574(7780), 663–666, https://doi.org/10.1038/s41586-019-1692-3, 2019.

Data format
Worksheet 1: CO2 predictions 0 to 1.8 Mya
Column 1: Age in thousands of years before 1950 AD (ka b1950)
Column 2: delta 18O_calcite of the LR04 (Lisiecki and Raymo, 2005) benthic stack, binned to 3,0000 year time steps (per mil)
Column 3: Predicted atmospheric CO2 concentration (ppm)
Column 4: Lower bound of predicted atmospheric CO2 concentration from bootstrap analysis (ppm)
Column 4: Upper bound of predicted atmospheric CO2 concentration from bootstrap analysis (ppm)
Worksheet 2: CO2 predictions 1.8 to 5.3 Mya
Column 1: Age in thousands of years before 1950 AD (ka b1950)
Column 2: delta 18O_calcite of the LR04 (Lisiecki and Raymo, 2005) benthic stack, binned to 3,0000 year time steps (per mil)
Column 3: Predicted atmospheric CO2 concentration (ppm)
Column 4: Lower bound of predicted atmospheric CO2 concentration from bootstrap analysis (ppm)
Column 4: Upper bound of predicted atmospheric CO2 concentration from bootstrap analysis (ppm)
Worksheet 3: Model 'R Project' code

Lineage

Progress Code: completed

Statement: Dates in temporal coverage correspond to the running time of the project.