15 Nov 2022
 | 15 Nov 2022
Status: a revised version of this preprint is currently under review for the journal CP.

Atlantic circulation changes across a stadial-interstadial transition

Claire Waelbroeck, Jerry Tjiputra, Chuncheng Guo, Kerim H. Nisancioglu, Eystein Jansen, Natalia Vazquez Riveiros, Samuel Toucanne, Frédérique Eynaud, Linda Rossignol, Fabien Dewilde, Elodie Marchès, Susana Lebreiro, and Silvia Nave

Abstract. We combine consistently dated benthic carbon isotopic records distributed over the entire Atlantic Ocean with numerical simulations performed by a glacial configuration of the Norwegian Earth System Model with active ocean biogeochemistry, in order to interpret the observed Cibicides δ13C changes at the stadial-interstadial transition corresponding to the end of Heinrich Stadial 4 (HS4) in terms of ocean circulation and remineralization changes. We show that the marked increase in Cibicides δ13C observed at the end of HS4 between ~2000 and 4200 m in the Atlantic can be explained by changes in nutrient concentrations as simulated by the model in response to the halting of freshwater input in the high latitude glacial North Atlantic. Our model results show that this Cibicides δ13C signal is associated with changes in the ratio of southern-sourced (SSW) versus northern-sourced (NSW) water masses at the core sites, whereby SSW is replaced by NSW as a consequence of the resumption of deep water formation in the northern North Atlantic and Nordic Seas after the freshwater input is halted. Our results further suggest that the contribution of ocean circulation changes to this signal increases from ~40 % at 2000 m to ~80 % at 4000 m. Below ~4200 m, the model shows little ocean circulation change but an increase in remineralization across the transition marking the end of HS4. The simulated lower remineralization during stadials than interstadials is particularly pronounced in deep subantarctic sites, in agreement with the decrease in the export production of carbon to the deep Southern Ocean during stadials found in previous studies.

Claire Waelbroeck 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-2022-83', Anonymous Referee #1, 22 Dec 2022
    • AC1: 'Reply on RC1', Claire Waelbroeck, 15 Feb 2023
    • AC2: 'Reply on RC1', Claire Waelbroeck, 15 Feb 2023
  • RC2: 'Comment on cp-2022-83', Anonymous Referee #2, 27 Dec 2022
    • AC1: 'Reply on RC1', Claire Waelbroeck, 15 Feb 2023
    • AC2: 'Reply on RC1', Claire Waelbroeck, 15 Feb 2023
  • RC3: 'Comment on cp-2022-83', Anonymous Referee #1, 31 Dec 2022
    • AC1: 'Reply on RC1', Claire Waelbroeck, 15 Feb 2023

Claire Waelbroeck et al.

Claire Waelbroeck et al.


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Short summary
The precise geometry of Atlantic circulation changes that accompanied rapid climate changes of the last glacial period is still unknown. Here we combine carbon isotopic records from 18 Atlantic sediment cores with numerical simulations performed by the Norwegian Earth System Model, in order to interpret the observed isotopic changes across a cold to warm transition. Our results show that the replacement of southern-sourced by northern-sourced water plays a dominant role below ~3000 m depth.