Decadal changes in the CaCO3 saturation state along 179°E in the Pacific Ocean

To assess degrees of ocean acidification, we mainly investigated decadal changes in the saturation state of sea-water with respect to aragonite (Omega(arg)), which is a more vulnerable mineral form of CaCO3, along the 179 degrees E meridian (WOCE P14N) in the Pacific Ocean. We found a maximum decrease of Omega(arg) of -0.48 (-0.034 a(-1)) at 200-300 dbar (isopycnal surfaces of 24.0-25.8 kg m(-3)) at 20 degrees N. Between 1993 and 2007, the saturation horizon rose by 17 dbar (1.2 dbar a(-1)) at latitudes 10 degrees N-50 degrees N. Although Delta Omega(arg) mostly reflected changes in normalized dissolved inorganic carbon (Delta nC(T)), it was larger than could be explained by anthropogenic CO2 storage alone. Decomposition of Delta nC(T) revealed that Delta Omega(arg) was enhanced by approximately 50% by a non-anthropogenic CO2 contribution represented by changes in apparent oxygen utilization. Our results suggest that ocean acidification can be temporarily accelerated by temporal changes in oceanic conditions. Citation: Murata, A., and S. Saito (2012), Decadal changes in the CaCO3 saturation state along 179 degrees E in the Pacific Ocean, Geophys. Res. Lett., 39, L12604, doi:10.1029/2012GL052297.