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 (C_ant). 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), C_ant and natural DIC (DIC_nat) 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, C_ant 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, C_ant and DIC_nat we achieved the following conclusions. The budget of DIC_nat 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 C_ant from the subtropics. These results demonstrate that the C_ant is accumulating in the SPNA without affecting the natural carbon cycle.