Changes in column inventories of carbon and oxygen in the Atlantic Ocean

[摘要] Increasing concentrations of dissolved inorganic carbon (DIC) in theinterior ocean are expected as a direct consequence of increasingconcentrations of CO₂ in the atmosphere. This extra DIC is oftenreferred to as anthropogenic carbon (C_ant), and its inventory, orincrease rate, in the interior ocean has previously been estimated by amultitude of observational approaches. Each of these methods is associatedwith hard to test assumptions since C_ant cannot be directly observed.Results from a simpler concept with fewer assumptions applied to theAtlantic Ocean are reported on here using two large data collections ofcarbon relevant bottle data. The change in column inventory on decadal timescales, i.e. the storage rate, of DIC, respiration compensated DIC andoxygen is calculated for the Atlantic Ocean. We report storage rates and theconfidence intervals of the mean trend at the 95% level (CI), reflectingthe mean trend but not considering potential biasing effects of the spatialand temporal sampling. For the whole Atlantic Ocean the mean trends for DICand oxygen are non-zero at the 95% confidence level: DIC: 0.86 (CI: 0.72–1.00)and oxygen: −0.24 (CI: −0.41–(−0.07)) mol m⁻² yr⁻¹. Foroxygen, the whole Atlantic trend is dominated by the subpolar NorthAtlantic, whereas for other regions the O₂ trends are not significant. Thestorage rates are similar to changes found by other studies, although withlarge uncertainty. For the subpolar North Atlantic the storage rates showsignificant temporal and regional variation of all variables. This seems tobe due to variations in the prevalence of subsurface water masses withdifferent DIC and oxygen concentrations leading to sometimes different signsof storage rates for DIC compared to published C_ant estimates. Thisstudy suggest that accurate assessment of the uptake of CO₂ by theoceans will require accounting not only for processes that influenceC_ant but also additional processes that modify CO₂ storage.

[学科分类] 地球化学与岩石