U.S. Dept. of Commerce / NOAA / OAR / PMEL / Publications

Impact of Anthropogenic CO2 on the CaCO3 System in the Oceans

Richard A. Feely1*, Christopher L. Sabine1, Kitack Lee2, Will Berelson3, Joanie Kleypas4, Victoria J. Fabry5, Frank J. Millero6

1Pacific Marine Environmental Laboratory, National Oceanic and Atmospheric Administration, Seattle, WA 98115–6349, USA
2School of Environmental Science and Engineering, Pohang University of Science and Technology, San 31, Nam-gu, Hyoja-dong, Pohang, 790–784, Republic of Korea
3Department of Earth Sciences, University of Southern California, Los Angeles, Los Angeles, CA 90089–0740, USA
4Environmental and Societal Impacts Group, National Center for Atmospheric Research, Boulder, CO 80307–3000, USA
5Department of Biological Sciences, California State University San Marcos, San Marcos, CA 92096–0001, USA
6University of Miami/Rosenstiel School of Marine and Atmospheric Sciences, Miami, FL, USA

Science, 305(5682), 362–366 (2004)
Copyright ©2004 by The American Association for the Advancement of Science. Further electronic distribution is not allowed.

Gallery of Figures

Figure 1

Fig. 1. (A) Atmospheric CO emission scenario and concentrations based on the Los Alamos National Laboratory general circulation model after Caldeira and Wickett [Caldeira and Wickett, 2003]. Gt, gigatons. (B) Relation between the concentrations of carbonate species in surface waters at constant salinity and TA for surface waters spanning the approximate range of temperatures observed in the oceans as a function of the surface ocean pCO in atm. The solid vertical light green line shows the range of carbonate ion concentrations observed in the present-day oceans, and the solid vertical magenta line shows the range of dissolved inorganic carbon concentrations. The three sets of parallel horizontal lines show the equilibrium carbonate ion concentrations for magnesian calcite, aragonite, and calcite saturation, respectively.

Figure 2

Fig. 2. Distribution of (A) aragonite and (B) calcite saturation depth ( = 1) in the global oceans. The pressure effect on the solubility is estimated from the equation of Mucci [Mucci, 1983] that includes the adjustments to the constants recommended by Millero [Millero, 1995]. The level at which aragonite and calcite are in thermodynamic equilibrium is known as the saturation depth. When the degree of saturation, , is greater than 1, seawater is supersaturated with aragonite and calcite; conversely, seawater is undersaturated with respect to these minerals when < 1. This depth is significantly shallower for aragonite than for calcite, because aragonite is more soluble in seawater than calcite.

Figure 3

Fig. 3. Vertical distributions of anthropogenic CO concentrations in mol kg and the supersaturation/undersaturation horizons for aragonite and calcite along north-south transects in the (A) Atlantic, (B) Pacific, and (C) Indian Oceans.

Fig. 4. In situ CaCO dissolution rates plotted as a function of depth in the three major ocean basins.

Figure 5

Fig. 5. Schematic diagram of the CaCO budget for the global oceans. The values are in Pg of CaCOC year.

Table 1

Table 1. Sediment trap particulate CaCO dissolution fluxes in the Pacific Ocean. The difference between the mean carbonate flux in the upper trap and the lower trap defines the dissolution flux. In all but one of the deepwater cases, the CaCO flux collected in the midwater trap is higher than the carbonate flux collected in the deepwater trap. The dissolution rates are derived from the differences in CaCO sediment trap fluxes between the upper and lower sediment traps divided by the depth range between the traps.

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