Preprints
https://doi.org/10.5194/egusphere-2025-1218
https://doi.org/10.5194/egusphere-2025-1218
26 Mar 2025
 | 26 Mar 2025

Northern North Atlantic climate variability controls on ocean carbon sinks in EC-Earth3-CC

Anna Pedersen, Carolin R. Löscher, and Steffen M. Olsen

Abstract. The northern North Atlantic is an important net sink of atmospheric CO2, though air-sea CO2 fluxes exhibit substantial variability across different timescales. The underlying drivers of this variability remain poorly understood across both temporal and regional scales. Here, we investigate interannual to decadal CO2 flux variability in the northern North Atlantic using historical simulations from the EC-Earth3-CC model. We assess the role of key dynamical and physical processes in shaping CO2 flux variability across five regions: the Nordic Seas, eastern Nordic Seas, the eastern and western subpolar North Atlantic, and the full North Atlantic. Our analysis reveals that physical parameters—including sea ice concentration (SIC), sea surface temperature (SST), sea surface salinity (SSS), and wind stress—along with dynamical processes related to ocean mixing and circulation, play a central role in regulating CO2 flux variability. Using regression analysis, we demonstrate that these drivers exert regionally and temporally varying influences, with our models achieving high R2 values indicating a strong degree of explanation for CO2 flux variability. The regression models capture interannual variability more effectively than decadal variability, highlighting the dominant role of short-term fluctuations in shaping CO2 flux dynamics. Overall, our results demonstrate that the predictors of CO2 flux variability are both spatially and temporally dependent. We find that CO2 flux variability cannot be fully explained by simple linear correlations with individual predictors but instead arises from complex interactions among multiple physical and dynamical processes. Notably, CO2 flux variability is particularly sensitive to changes in certain predictors, such as wind stress, consistent with expectations based on the gas transfer equation used to compute air-sea CO2 fluxes.

Competing interests: At least one of the (co-)authors is a member of the editorial board of Biogeosciences. The peer-review process was guided by an independent editor, and the authors also have no other competing interests to declare.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this paper. While Copernicus Publications makes every effort to include appropriate place names, the final responsibility lies with the authors. Views expressed in the text are those of the authors and do not necessarily reflect the views of the publisher.
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Journal article(s) based on this preprint

26 Sep 2025
Northern North Atlantic climate variability controls on ocean carbon sinks in EC-Earth3-CC
Anna Pedersen, Carolin R. Löscher, and Steffen M. Olsen
Biogeosciences, 22, 5009–5029, https://doi.org/10.5194/bg-22-5009-2025,https://doi.org/10.5194/bg-22-5009-2025, 2025
Short summary
Anna Pedersen, Carolin R. Löscher, and Steffen M. Olsen

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2025-1218', Anonymous Referee #1, 25 Apr 2025
    • AC1: 'Reply on RC1', Anna Pedersen, 23 May 2025
  • RC2: 'Comment on egusphere-2025-1218', Anonymous Referee #2, 25 Apr 2025
    • AC2: 'Reply on RC2', Anna Pedersen, 23 May 2025

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2025-1218', Anonymous Referee #1, 25 Apr 2025
    • AC1: 'Reply on RC1', Anna Pedersen, 23 May 2025
  • RC2: 'Comment on egusphere-2025-1218', Anonymous Referee #2, 25 Apr 2025
    • AC2: 'Reply on RC2', Anna Pedersen, 23 May 2025

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload
ED: Reconsider after major revisions (26 May 2025) by Peter Landschützer
AR by Anna Pedersen on behalf of the Authors (23 Jun 2025)  Author's response   Author's tracked changes   Manuscript 
ED: Referee Nomination & Report Request started (24 Jun 2025) by Peter Landschützer
RR by Anonymous Referee #1 (30 Jun 2025)
ED: Publish as is (10 Jul 2025) by Peter Landschützer
AR by Anna Pedersen on behalf of the Authors (12 Jul 2025)

Journal article(s) based on this preprint

26 Sep 2025
Northern North Atlantic climate variability controls on ocean carbon sinks in EC-Earth3-CC
Anna Pedersen, Carolin R. Löscher, and Steffen M. Olsen
Biogeosciences, 22, 5009–5029, https://doi.org/10.5194/bg-22-5009-2025,https://doi.org/10.5194/bg-22-5009-2025, 2025
Short summary
Anna Pedersen, Carolin R. Löscher, and Steffen M. Olsen
Anna Pedersen, Carolin R. Löscher, and Steffen M. Olsen

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Short summary
The North Atlantic plays a crucial role in absorbing atmospheric CO2, but its air-sea CO2 flux varies across time and space. Using historical climate model simulations, we investigate how physical and oceanic processes drive the variability. Our results show that sea ice, temperature, salinity, wind stress, and ocean circulation shape CO2 exchange, with short-term fluctuations playing a dominant role. Understanding these complex interactions is key to predicting future ocean carbon uptake.
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