Mechanisms of Air-sea CO₂ Exchange in the Central Baltic Sea

Wind speed is widely used to parameterise air-sea carbon dioxide (CO₂) transfer velocity (K), but a new study by Dong et al. (2026) shows that K is also directly affected by surface conditions. Using eddy covariance and dual-tracer methods in the central Baltic Sea, researchers observed K ~30% lower than in the open ocean under similar winds. This reduction is mainly due to limited fetch and high surfactant concentrations. In the Baltic Sea, short fetch restricts wave development, reducing breaking and bubble-mediated exchange. Meanwhile, biologically produced surfactants accumulate at the surface, dampening turbulence and inhibiting gas exchange. These findings are critical for coastal carbon budgets and have direct implications for mCDR (often operated in the coastal ocean), where accurate estimates of air-sea CO₂ exchange are essential for MRV.

Reference: Dong, Y., Marandino, C.A., Dobashi, R., et al. (2026). Mechanisms of air-sea CO₂ exchange in the central Baltic Sea. Atmos. Chem. Phys., 26, 5567–5587.
https://doi.org/10.5194/acp-26-5567-2026