A new study supported by ObsSea4Clim and the SDU’s climate cluster focuses on describing the climate variability controls on ocean carbon sinks in the EC-Earth3-CC.

The northern North Atlantic (NA) is an important net sink of atmospheric CO₂, though atmosphere–ocean 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 NA 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 (NS), eastern NS, the eastern and western subpolar NA, and the full NA. 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 atmosphere–ocean CO₂ fluxes.

Cite as:

Pedersen, A., Löscher, C. R., and Olsen, S. M.: Northern North Atlantic climate variability controls on ocean carbon sinks in EC-Earth3-CC, Biogeosciences, 22, 5009–5029, https://doi.org/10.5194/bg-22-5009-2025, 2025.Received: 14 Mar 2025

 – Discussion started: 26 Mar 2025

 – Revised: 23 Jun 2025

 – Accepted: 10 Jul 2025

 – Published: 26 Sep 2025

Anna Pedersen was supported by SDU’s climate cluster, EU Horizon Ocean observations and indicators for climate and assessments, ObsSea4Clim (grant no. 101136548), 10.3030/101136548 internal contribution no. 15, NCKF/DMI, by the Villum Foundation (grant no. 29411), and by Danmarks Fri Forskningsfond (DFF, Carolin R. Löscher, grant no. 4283-00265B).