28 Jun 2022
 | 28 Jun 2022
Status: a revised version of this preprint is currently under review for the journal CP.

Impact of iron fertilisation on atmospheric CO2 during the last glaciation

Himadri Saini, Katrin J. Meissner, Laurie Menviel, and Karin Kvale

Abstract. While several processes have been identified to explain the decrease in atmospheric CO2 during glaciations, a better quantification of the contribution of each of these processes is needed. For example, enhanced aeolian iron input into the ocean during glacial times has been suggested to drive a 5 to 28 ppm atmospheric CO2 decrease. Here, we constrain this contribution by performing a set of sensitivity experiments with different aeolian iron input patterns and iron solubility factors under boundary conditions corresponding to 70 thousand years before present (70 ka BP), a time period characterised by the first observed peak in glacial dust flux. We show that the decrease in CO2 as a function of the Southern Ocean iron input follows an exponential decay relationship. This exponential decay response arises due to the saturation of the biological pump efficiency and levels out at ∼21 ppm in our simulations. Using a best estimate of surface water iron solubility between 3 and 5 %, a ∼9 to 11 ppm CO2 decrease is simulated at 70 ka BP, while a plausible range of CO2 draw-down between 4 to 16 ppm is obtained using the wider but possible range of 1 to 10 %. This would account for ∼12–50 % of the reconstructed decrease in atmospheric CO2 (∼32 ppm) between 71 and 64 ka BP. We further find that in our simulations the decrease in atmospheric CO2 concentrations is solely driven by iron fluxes south of the Antarctic polar front, while iron fertilization elsewhere plays a negligible role.

Himadri Saini et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on cp-2022-46 by Juan Muglia', Juan Muglia, 12 Sep 2022
  • RC2: 'Comment on cp-2022-46', Anonymous Referee #2, 13 Oct 2022
  • RC3: 'Comment on cp-2022-46', Anonymous Referee #3, 17 Oct 2022

Himadri Saini et al.

Himadri Saini et al.


Total article views: 822 (including HTML, PDF, and XML)
HTML PDF XML Total BibTeX EndNote
571 223 28 822 13 12
  • HTML: 571
  • PDF: 223
  • XML: 28
  • Total: 822
  • BibTeX: 13
  • EndNote: 12
Views and downloads (calculated since 28 Jun 2022)
Cumulative views and downloads (calculated since 28 Jun 2022)

Viewed (geographical distribution)

Total article views: 749 (including HTML, PDF, and XML) Thereof 749 with geography defined and 0 with unknown origin.
Country # Views %
  • 1
Latest update: 29 Mar 2023
Short summary
Understanding the variability in atmospheric CO2 during the past glacial cycle is crucial to understand the future impact of climate change. Previous research has hypothesised a key role of higher iron input into the Southern Ocean in influencing the global atmospheric CO2 levels by impacting the changes in the marine phytoplankton response. In this study we test this hypothesis using climate modelling and constraint the impact of ocean iron influence on global CO2 decrease.