Budgets of Dissolved Inorganic Carbon in the Eastern Subpolar North Atlantic in the 2000s from In Situ Data

The subpolar North Atlantic (SPNA) is determinant in the global carbon cycle because of the deep water ventilation processes lead to both high uptake of atmospheric CO2 and large inventories of anthropogenic CO2 (Cant). Hence, it is crucial to know its response to the increasing anthropogenic pressure. We provide here new estimates of storage rate and lateral advection of dissolved inorganic carbon (DIC), Cant and natural DIC (DICnat) in the eastern-SPNA in the 2000s using in situ data, mainly from the OVIDE section. We also yield estimates of air-sea fluxes of CO2, Cant and natural CO2, as well as the consumption of DIC by the biological activity in this oceanic region. These estimates are essential to be used as benchmark for the modeler community. From the analysis jointly of the budgets of DIC, Cant and DICnat we achieved the following conclusions. The budget of DICnat is found in steady state, confirming a long-standing hypothesis with in situ data for the first time. The biological activity, consuming CO2, is driving the uptake of natural CO2 from the atmosphere. The CO2 increase in the ocean due to anthropogenic activities is the sole responsible of the DIC storage rate which is chiefly explained by advection of Cant from the subtropics. These results demonstrate that the Cant is accumulating in the SPNA without affecting the natural carbon cycle.