To assess degrees of ocean acidification, we mainly investigated decadal changes in the saturation state of seawater with respect to aragonite (Ωarg), which is a more vulnerable mineral form of CaCO3, along the 179°E meridian (WOCE P14N) in the Pacific Ocean. We found a maximum decrease of Ωarg of −0.48 (−0.034 a−1) at 200–300 dbar (isopycnal surfaces of 24.0–25.8 kg m−3) at 20°N. Between 1993 and 2007, the saturation horizon rose by 17 dbar (1.2 dbar a−1) at latitudes 10°N–50°N. Although ΔΩarg mostly reflected changes in normalized dissolved inorganic carbon (ΔnCT), it was larger than could be explained by anthropogenic CO2 storage alone. Decomposition of ΔnCT revealed that ΔΩarg 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.
Posts Tagged 'Pacific'
Tags: chemistry, field, Pacific
Tags: chemistry, Pacific
The Hawaiian archipelago, the most remote group of islands on Earth, has long been associated with the world’s most recognizable image of global change. The Mauna Loa atmospheric CO2 record, begun in March 1958 by Charles David Keeling, shows with startling clarity the saw-tooth pattern of the seasonal changes of land vegetation, and the still astonishing, dominating, rise forced by fossil fuel burning which is rapidly changing our world. Within perhaps only 5 years the peak in the annual signal atop Mauna Loa will touch the 400 ppm by volume mark, which would have been inconceivable to scientists of the first half of the twentieth century. But there is one huge and environmentally critical signal that is not easily seen in the “Keeling curve,” and that is the oceanic uptake of fossil fuel CO2. In this issue of PNAS, Dore et al. (1) document with great clarity the changes in ocean CO2 chemistry and pH occurring in the ocean in the waters off Hawaii from fossil fuel CO2 invasion.