15 Nov 2022
15 Nov 2022
Status: this preprint is currently under review for the journal CP.

Atlantic circulation changes across a stadial-interstadial transition

Claire Waelbroeck1, Jerry Tjiputra2, Chuncheng Guo2, Kerim H. Nisancioglu3, Eystein Jansen2,3, Natalia Vazquez Riveiros4, Samuel Toucanne4, Frédérique Eynaud5, Linda Rossignol5, Fabien Dewilde6, Elodie Marchès7, Susana Lebreiro8, and Silvia Nave9 Claire Waelbroeck et al.
  • 1LOCEAN/IPSL, Sorbonne Université-CNRS-IRD-MNHN, UMR7159, 75005 Paris, France
  • 2NORCE Norwegian Research Centre, Bjerknes Centre for Climate Research, 5007 Bergen, Norway
  • 3Department of Earth Science, University of Bergen, Bjerknes Centre for Climate Research, 5007 Bergen, Norway
  • 4Geo-Ocean, University of Brest, CNRS, IFREMER, UMR6538, 29280 Plouzané, France
  • 5UMR-CNRS 5805 EPOC - OASU, University of Bordeaux, 50023 Pessac, France
  • 6IUEM, UMS3113, 29280 Plouzané, France
  • 7Service Hydrographique et Océanographique de la Marine, 29228 Brest, France
  • 8Instituto Geológico y Minero de España (IGME)-CSIC, 28003 Madrid, Spain
  • 9LNEG, I.P., UGHGC, 2610-999 Amadora, Portugal

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: open (until 10 Jan 2023)

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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.