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

• Published in: Biogeosciences
• Main Authors: Tanhua, Toste, Keeling, R. F.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications (EGU) 2012
• Subjects: North Atlantic
• Online Access: https://oceanrep.geomar.de/id/eprint/15423/; https://oceanrep.geomar.de/id/eprint/15423/1/bg-9-4819-2012.pdf; http://www.biogeosciences.net/9/4819/2012/; https://doi.org/10.5194/bg-9-4819-2012

Increasing concentrations of dissolved inorganic carbon (DIC) in the interior ocean is expected as a direct consequence of increasing concentrations of CO2 in the atmosphere. This extra DIC is often referred to as anthropogenic carbon (Cant), and its inventory, or increase rate, in the interior ocean has previously been estimated by a multitude of observational approaches. Each of these methods are associated with hard to test assumptions since Cant cannot be directly observed. Results from a simpler concept with few assumptions applied to the Atlantic Ocean are reported on here using two large data collections of carbon relevant bottle data. The change in column inventory on decadal time scales, i.e. the storage rate, of DIC, respiration compensated DIC and oxygen is calculated for the Atlantic Ocean. The average storage rates for DIC and oxygen is calculated to 0.72 ± 1.22 (95% confidence interval of the mean trend: 0.65–0.78) mol m−2 yr−1 and −0.54 ± 1.64 (95% confidence interval of the mean trend: –0.64–(−0.45)) mol m−2 yr−1, respectively, for the Atlantic Ocean, where the uncertainties reflect station-to-station variability and where the mean trends are non-zero at the 95% confidence level. The standard deviation mainly reflects uncertainty due to regional variations, whereas the confidence interval reflects the mean trend. The storage rates are similar to changes found by other studies, although with large uncertainty. For the subpolar North Atlantic the storage rates show significant temporal variation of all variables. This seems to be due to variations in the prevalence of subsurface water masses with different DIC concentrations leading to sometimes different signs of storage rates for DIC and Cant. This study suggest that accurate assessment of the uptake of CO2 by the oceans will require accounting not only for processes that influence Cant but also additional processes that modify CO2 storage.