01. Summary of the project

Recent evaluations of the CO2 uptake in the North Atlantic showed that the natural component of the carbon cycle has been affected by the variability of the Meridional Overturning Circulation (MOC). The first goal of BOCATS is to extend the time series of MOC and water ventilation observations to better quantify their effects on the carbon cycle in the North Atlantic on decadal time scales. The estimation of this variability is essential to evaluate the future scenarios of climate changes. The second goal of BOCATS is to evaluate the effect of present atmospheric CO2 increase in the CaCO3 production and dissolution. Recent estimates of acidification in the North Atlantic show a significant effect in deep waters that have a potential impact on calcareous organisms and call into question the generally accepted hypothesis of steady-state CaCO3 cycle. The objectives of BOCATS are addressed through two main activities: i) Continuation of the decadal monitoring of the circulation and carbon cycle in the subpolar North Atlantic with the 9th occupation of the A25 hydrography/geochemistry section from Portugal to Greenland that was first occupied in 1997. ii) Evaluation of the variability of the carbon cycle in the subpolar gyre separating between natural and anthropogenic components and including organic matter, sediments and other biogenic elements. A major observational contribution of BOCATS will be a cruise to carry out in June-July 2016. The planned high quality observations in the subpolar gyre will contribute to the early detection of the alteration of the carbon cycle and will allow the accurate estimation of the rates of CO2 storage and acidification, relating these changes with the variability of the MOC.