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

N. R. Bates, M. H. P. Best, K. Neely, R. Garley, A. G. Dickson, R. J. Johnson
2012 Biogeosciences  
<p><strong>Abstract.</strong> Fossil fuel use, cement manufacture and land-use changes are the primary sources of anthropogenic carbon dioxide (CO<sub>2</sub>) to the atmosphere, with the ocean absorbing approximately 30% (Sabine et al., 2004). Ocean uptake and chemical equilibration of anthropogenic CO<sub>2</sub> with seawater results in a gradual reduction in seawater pH and saturation states (&amp;Omega;) for calcium carbonate (CaCO<sub>3</sub>) minerals in a process termed ocean
more » ... on. 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<sub>2</sub> changes and ocean acidification in the North Atlantic subtropical gyre near Bermuda from 1983–2011. Dissolved inorganic carbon (DIC) and partial pressure of CO<sub>2</sub> (<i>p</i>CO<sub>2</sub>) increased in surface seawater by ~40 μmol kg<sup>−1</sup> and ~50 μatm (~20%), respectively. Increasing Revelle factor (<i>β</i>) values imply that the capacity of North Atlantic surface waters to absorb CO<sub>2</sub> has also diminished. As indicators of ocean acidification, seawater pH decreased by ~0.05 (0.0017 yr<sup>&amp;minus;1</sup>) and &amp;omega; values by ~7–8%. Such data provide critically needed multi-decadal information for assessing the North Atlantic Ocean CO<sub>2</sub> sink and the pH changes that determine marine ecosystem responses to ocean acidification.</p>
doi:10.5194/bg-9-2509-2012 fatcat:isicyt6wzregphzkccqb5dbgpe