Work

Air-sea CO2 exchange in the Eastern Atlantic and the Mediterranean Sea based on autonomous surface measurements

Year: 2025

Type: article

Abstract: Introduction The ATL2MED mission, conducted between October 2019 and July 2020, investigated the variability of air–sea CO 2 exchange in the Eastern Atlantic and the Mediterranean Sea. The main objectives were to assess the spatial and temporal variability of the seawater partial pressure of CO 2 ( p CO 2sw ), identify its controlling physical and biogeochemical processes, estimate the CO 2 fluxes across the sea–air interface, and evaluate the performance of neural network-based predictions (CANYON-MED) in contrasting oceanographic regions. Methods High-resolution autonomous measurements were collected using Saildrone Unmanned Surface Vehicles (USVs), complemented by fixed ocean stations, gliders, and research vessels. Data quality was ensured through cross-validation among platforms, despite challenges such as sensor drift caused by biofouling. Results The results reveal pronounced regional differences in p CO 2sw and CO 2 fluxes, driven by thermal effects, biological activity, and physical mixing. In the Eastern Atlantic, upwelling systems off northwest Africa induced strong outgassing, while the western Mediterranean acted as a CO 2 sink during the spring bloom. Conversely, the Adriatic Sea exhibited episodic CO 2 outgassing, particularly in its southern and northern basins, associated with thermal stratification, river plumes, and coastal upwelling. Discussion Saildrone measurements successfully resolved sub-mesoscale processes typically missed by fixed platforms, demonstrating their potential to enhance ocean CO 2 observations in under-sampled or logistically constrained regions. The good agreement with neural network-based estimates further supports the robustness of the dataset. Overall, these findings emphasize the value of high-resolution, multi-platform approaches for accurately quantifying CO 2 fluxes and improving predictive capabilities in a changing ocean.

Source: Frontiers in Marine Science

DOI: 10.3389/fmars.2025.1633617