Preprints
https://doi.org/10.5194/cp-2021-62
https://doi.org/10.5194/cp-2021-62
17 Jun 2021
 | 17 Jun 2021
Status: this discussion paper is a preprint. It has been under review for the journal Climate of the Past (CP). The manuscript was not accepted for further review after discussion.

Revised alkenone δ13C based CO2 estimates during the Plio-Pleistocene

Osamu Seki and James Bendle

Abstract. Here we revisit reported alkenone δ13C (δ13CC37) based CO2 records during the Plio-Pleistocene and apply a refined approach to better constrain the dynamic range of CO2 during the time. Specifically, we consider ways to correct for regional differences in physical oceanographic factors. As a result of our relatively simple approach we find that offsets of ~150 ppm between reported δ13CC37 CO2 records from different sites can be significantly reduced. This confirms that better constraints on environmental variables, including physical oceanographic controls on depth and season of production are key aspects for improving δ13CC37 based CO2 estimates. The revised δ13CC37 CO2 datasets suggest that Plio-Pleistocene CO2 levels are 180–350 ppm, which is consistent with the most of reported CO2 reconstructions, though their upper end of Pliocene CO2 levels are lower than that of some CO2 estimates.

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Osamu Seki and James Bendle

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on cp-2021-62', Anonymous Referee #1, 22 Jul 2021
  • RC2: 'Comment on cp-2021-62', Anonymous Referee #2, 26 Jul 2021

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on cp-2021-62', Anonymous Referee #1, 22 Jul 2021
  • RC2: 'Comment on cp-2021-62', Anonymous Referee #2, 26 Jul 2021
Osamu Seki and James Bendle
Osamu Seki and James Bendle

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Short summary
The reconstruction of CO2 levels in the past is a crucial objective in palaeoclimate research. However, estimates of CO2 level markedly differ among the data. We revised reported alkenone δ13C based CO2 records from the Pliocene to Pleistocene based on a refined approach. Our approach significantly reduced the large offsets between reported alkenone δ13C CO2 records, confirming that better constraints on environmental variables are key aspects for improving alkenone δ13C based CO2 estimates.