BOCATS2, a continuation of the previous BOCATS project (2014-2017), will be a main contribution to the observation of the NA subpolar gyre by continuing the occupation of the biennial section A25-Ovide (2021 and 2023) within the framework of the international GO-SHIP programme. A particular focus will be given to the new challenge of assessing the variability of the deep circulation in the NA, improving the spatial-temporal resolution of deep currents and water mass characteristics by deploying a regional deep-ARGO array and, at a submilenary scale, using paleoceanographic data obtained in sedimentary records from key sites, such as the Bight and Charlie-Gibbs fracture zones. The high-quality observations foreseen in the SPNA will contribute to the early detection of the alteration of the carbon cycle allowing the precise estimation of the heat, CO2 and N2O storage rates and, ultimately, to find the connection between these changes and the variability of the AMOC at different time scales. The natural and anthropogenic fluxes of heat, CO2 and N2O will be evaluated, as well as the present and submillenary scale transport of sediments and biogenic elements, and the impact of acidification on these timescales by means of the analysis of CaCO3 and organic carbon fluxes to the sediment. Besides, the current ocean acidification rates will also be quantified by evaluating the present situation and establishing future projections. These new observation-based estimates will be a valuable result that will be used to validate the predictions from the models (GCMs and ESMs from CMIP5-6) for the 2°C warming scenario. Finally, special attention will be paid to the rates of elevation of aragonite saturation horizons in deep layers, where the impact on the ecosystems sustained by calcareous organisms is potentially imminent

Oceanographic data acquired during the BOCATS-2-2023_LEG1 Cruise (29SG20230608) on board the ResearchVessel Sarmiento de Gamboa in 2023