Detecting anthropogenic carbon dioxide uptake and ocean acidification in the North Atlantic Ocean

• Published in: Biogeosciences
• Main Authors: Bates, N. R., Best, M. H. P., Neely, K., Garley, R., Dickson, A. G., Johnson, R. J.
• Format: Text
• Language: English
• Published: 2018
• Subjects: North Atlantic; Ocean acidification
• Online Access: https://doi.org/10.5194/bg-9-2509-2012; https://www.biogeosciences.net/9/2509/2012/

Fossil fuel use, cement manufacture and land-use changes are the primary sources of anthropogenic carbon dioxide (CO 2 ) to the atmosphere, with the ocean absorbing approximately 30% (Sabine et al., 2004). Ocean uptake and chemical equilibration of anthropogenic CO 2 with seawater results in a gradual reduction in seawater pH and saturation states (Ω) for calcium carbonate (CaCO 3 ) minerals in a process termed ocean acidification. Assessing the present and future impact of ocean acidification on marine ecosystems requires detection of the multi-decadal rate of change across ocean basins and at ocean time-series sites. Here, we show the longest continuous record of ocean CO 2 changes and ocean acidification in the North Atlantic subtropical gyre near Bermuda from 1983–2011. Dissolved inorganic carbon (DIC) and partial pressure of CO 2 ( p CO 2 ) increased in surface seawater by ~40 μmol kg −1 and ~50 μatm (~20%), respectively. Increasing Revelle factor ( β ) values imply that the capacity of North Atlantic surface waters to absorb CO 2 has also diminished. As indicators of ocean acidification, seawater pH decreased by ~0.05 (0.0017 yr −1 ) and ω values by ~7–8%. Such data provide critically needed multi-decadal information for assessing the North Atlantic Ocean CO 2 sink and the pH changes that determine marine ecosystem responses to ocean acidification.