As CO continues to increase in the atmosphere, it is important to continue the work begun with the Global Survey of CO in the Ocean. Because CO is an acid gas, the uptake of anthropogenic CO consumes carbonate ions and lowers the pH of the ocean. The carbonate ion concentration of surface seawater in equilibrium with the atmosphere will decrease by about 30% and the hydrogen ion concentration will increase by about 70% with a doubling of atmospheric CO from pre-industrial levels (280 to 560 ppm). As the carbonate ion concentration decreases, the buffering capacity of the ocean and its ability to absorb more CO from the atmosphere is diminished. Over the long term (millennial time scales) the ocean has the potential to absorb as much as 85% of the anthropogenic CO that is released into the atmosphere. Because the lifetime of fossil fuel CO in the atmosphere ranges from decades to centuries, mankind's reliance on fossil fuel for heat and energy will continue to have a significant effect on the chemistry of the earth's atmosphere and oceans and therefore on our climate for many centuries to millennia.
Plans are being formulated in several countries, including the United States, to establish a set of repeat sections to document the increasing anthropogenic inventories in the oceans. Most of these sections will follow the lines occupied during the WOCE Hydrographic Programme on which JGOFS investigators made CO survey measurements. The current synthesis effort will provide an important baseline for assessment of future changes in the carbon system. The spatially extensive information from the repeat sections, together with the temporal records from the time-series stations and the spatial and temporal records available from automated surface pCO measurements on ships of opportunity, will greatly improve our understanding of the ocean carbon system and provide better constraints on potential changes in the future.
The authors are grateful to the members of the CO Science Team and the JGOFS and WOCE investigators for making their data available for this work. We thank Lisa Dilling of the National Oceanic and Atmospheric Administration (NOAA) Office of Global Programs, Don Rice of the National Science Foundation and Mike Riches of the Department of Energy (DOE) for their efforts in coordinating this research. This work was supported by DOE and NOAA as a contribution to the U.S. JGOFS Synthesis and Modeling Project (Grant No. GC99-220) and by grants to Taro Takahashi from NSF (OPP-9506684) and NOAA (NA16GP01018). This publication was supported by the Joint Institute for the Study of the Atmosphere and Ocean (JISAO) under NOAA Cooperative Agreement #NA67RJO155, Contribution #832, and #2331 from the NOAA/Pacific Marine Environmental Laboratory. This is U.S. JGOFS Contribution Number 683.
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