Figure 1. Schematic diagram of the carbon dioxide (CO) system in seawater. The 1 x CO concentrations are for a surface ocean in equilibrium with a pre-industrial atmospheric CO level of 280 ppm. The 2 x CO concentrations are for a surface ocean in equilibrium with an atmospheric CO level of 560 ppm. Current model projections indicate that this level could be reached sometime in the second half of this century. The atmospheric values are in units of ppm. The oceanic concentrations, which are for the surface mixed layer, are in units of µmol kg.
Figure 2. The Global Survey of CO in the Ocean: cruise tracks and stations occupied between 1991 and 1998.
Figure 3. Distribution of climatological mean sea-air pCO difference (pCO) for the reference year 1995 representing non-El Niño conditions in February (a) and August (b). These maps are based on about 940,000 measurements of surface water pCO from 1958 through 2000. The pink lines indicate the edges of ice fields. The yellow-red colors indicate regions with a net release of CO into the atmosphere, and the blue-purple colors indicate regions with a net uptake of CO from the atmosphere. The mean monthly atmospheric pCO value in each pixel in 1995, (pCO)air, is computed using (pCO)air = (CO)air × (Pb - pH2O). (CO)air is the monthly mean atmospheric CO concentration (mole fraction of CO in dry air) from the GLOBALVIEW database (2000); Pb is the climatological mean barometric pressure at sea level from the Atlas of Surface Marine Data (1994); and the water vapor pressure, pHO, is computed using the mixed layer water temperature and salinity from the World Ocean Database (1998) of NODC/NOAA. The sea-air pCO difference values in the reference year 1995 have been computed by subtracting the mean monthly atmospheric pCO value from the mean monthly surface ocean water pCO value in each pixel.
Figure 4. Graph of the different relationships that have been developed for the estimation of the gas transfer velocity, k, as a function of wind speed. The relationships were developed from wind-wave tank experiments, oceanic observations, global constraints and basic theory. The different forms of the relationships are summarized in Table 1. U is wind speed at 10 m above the sea surface.
Figure 5. Effects of the various gas transfer/wind speed relationships on the estimated air-sea exchange flux of CO in the ocean as a function of latitude. The global effects on the net air-sea flux are given in Table 1.
Figure 6. Distribution of the climatological mean annual sea-air CO flux (moles CO m yr) for the reference year 1995 representing non-El Niño conditions. This has been computed using the mean monthly distribution of sea-air pCO difference, the climatological NCEP 41-year mean wind speed and the wind-speed dependence of the CO gas transfer velocity of Wanninkhof (1992). The yellow-red colors indicate a region characterized by a net release of CO to the atmosphere, and the blue-purple colors indicate a region with a net uptake of CO from the atmosphere. This map yields an annual oceanic uptake flux for CO of 2.2 ± 0.4 Pg C yr.
Figure 7. Zonal mean pre-industrial distributions of dissolved inorganic carbon (in units of µmol kg) along north-south transects in the Atlantic, Indian and Pacific oceans. The Pacific and Indian Ocean data are from the Global CO Survey (this study), and the Atlantic Ocean data are from Gruber (1998).
Figure 8. Zonal mean distributions of estimated anthropogenic CO concentrations (in units of µmol kg) along north-south transects in the Atlantic, Indian and Pacific oceans. The Pacific and Indian Ocean data are from the Global CO Survey (this study), and the Atlantic Ocean data are from Gruber (1998).
Figure 9. Zonal mean anthropogenic CO inventories (in units of moles m) in the Atlantic, Indian and Pacific oceans.
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