The ocean, an essential element in the evolution of the climate, currently accumulates 93% of the excess heat and 31% of the excess CO2 generated by human activity. The European climate in general, and the Iberian Peninsula in particular, is influenced in a very relevant way by the southern return circulation (CRM), which transports the warm surface waters to the north and the cold deep waters #face the south and play a crucial role in the climate system, as it facilitates the redistribution of the planet’s heat, water and carbon dioxide. In fact, the southern return circulation significantly amplifies the uptake of anthropogenic CO2 (generated by human activity), exceeding the mean oceanic value by more than 50%. But there are several studies that confirm the recent weakening of this circulation, a phenomenon that according to the report of the Intergovernmental Panel for Climate Change (IPCC, 2019) is expected to be more pronounced in the coming decades.
However, the IPCC itself recognizes that there is a lack of observations to be able to quantify the magnitude of this reduction and it is in this context that the subproject Bocats2 arises (Biennial observation of carbon, acidification, transport and sedimentation in the North Atlantic) , led by CIM researchers Guillermo Francés (Geological and Bioxeochemical Oceanography group) and Gabriel Rosón (Physical Oceanography Group). The main objective of this initiative is “to continue with the observational monitoring (recent and past) of ocean circulation and acidification in the North Atlantic, essential to advance in the accurate detection of anthropogenic impact and to improve the projections of the adjusted climate models that support the IPCC reports for the subpolar turn of the North Atlantic (SPNA), a region known for its strong influence on the European climate.
Inserted in an extended project
Bocats2 is part of a larger project, coordinated by the Marine Research Institute (IIM, CSIC), and financed with 342,430 euros, of which 124,630 correspond to the subproject of the University of Vigo, within the framework of the Generation of Knowledge 2019 program of the Ministry of Science and Innovation. The main objective is to study the millennial and sub millennial variability of the deep currents through the channels that cross the Reykjanes ridge (Bight and Charlie-Gibbs fracture zones), in southwestern Iceland. These two fracture zones, especially the CGFZ, constitute the main deep-water communication routes between the western and eastern basins of the North Atlantic and their hydrography is largely unknown, both today and in the past, when they were under other global weather conditions. Bocats2 also intends to continue with the estimation of the flow of carbonate and organic carbon to the sediments, in the line of the previous project (Bocats), essential aspects related to the production, accumulation and preservation of these compounds (carbon cycle, acidification, etc.)
Two oceanographic campaigns
With the launch of this second part of the Bocats project, UVigo researchers will continue with the biennial program of observation of the water column and the study of new sedimentary records from key places such as the Bight and Charlie-Gibbs fracture zones. The project has planned two oceanographic campaigns, as the researchers explain, “one that will leave Vigo on May 28 and another in 2023″, both on board the B / El Sarmiento de Gamboa.
During the first parts of the campaigns, on the Vigo-Reykjavik route, “the measurements of the water column will be carried out within the framework of the international GO-SHIP program to evaluate the variability of the deep circulation of the North Atlantic and improve the spatio-temporal resolution of currents”. In addition, the high-quality observations provided in the SPNA will contribute to the early detection of the alteration of the carbon cycle and will allow the precise estimation of the storage rates of heat, CO2 and N2O, relating these changes to the variability of the CRM. In the second parts of the campaigns, that is, on the journey from Reykjavik to Vigo, “sedimentary soundings will be obtained to estimate the dynamics of the different time scales of the deep water masses and the connection between the basins through the areas of fracture during the Upper Pleistocene and the Holocene”.
In short, the researchers explain, “the fluxes, their natural and anthropogenic components, heat, CO2 and N2O, as well as current transport and the sub-millennial scale of sediments and bioxenic elements and the impact of acidification on these scales will be evaluated by analyzing the CaCO3 and organic carbon fluxes to the sediment “. In addition, the current rates of ocean acidification will be quantified, evaluating the present situation and establishing future projections that will allow comparing the results of the observations with the predictions of the models (GCMs and ESMs of CMIP5-6) for the 2º C warming scenario, with special emphasis on the rates of elevation of the aragonite saturation horizons in deep layers, where the impact is potentially imminent in the ecosystems supported by calcarium organisms ”.
An international team
The project’s research team, in addition to the researchers from the Geological and Bioxeochemical Oceanography and Physical Oceanography groups, has the contribution of specialists from the Instititut de Ciencias de el Mar (ICM, CSIC) and the Instituto Tecnolóxico do Mar (INTECMAR). , Xunta de Galicia). Researchers from the National Oceanography Center (NOC, UK), the Institut Français de Recherche pour l ‘Exploitation de la Mer (IFREMER, France), the University of Bremen (Germany) and the Royal Holloway University (UK) collaborate in the work team).
More information at DUVI