Carbonate marine gradient

Springer-Young M., Erickson D. J., and Carsey T. P. (1996) Carbon monoxide gradients in the marine botmdary layer of the North Atlantic Ocean. J. Geophys. Res. 101,4479-4484. 

Figure 9.1 Freshwater-marine mixing ratios of dissolved inorganic carbon (DIC) and isotopic composition (DI13C) across three different salinity gradients. Bottom isotopic change between — 10%e at the freshwater end-member, and +2%c at the marine end-member, both end-member values are based on concentration-weighted averages (data sources Spiker and Schemel, 1979 Spiker, 1980). (Modified from Fry, 2002.)...

Carbon monoxide (CO) is also formed in aquatic environments from the photochemical degradation of DOM [3,4,8,22,94-105]. Strong gradients of CO have been observed in the lowest 10 metres of the atmosphere over the Atlantic Ocean [97]. The samples nearest the ocean surface were some 50 ppb higher than at the 10-metre altitude-sampling inlet. This implies that the ocean is a source of CO to the atmosphere and that this source can increase the atmospheric concentration. CO is reactive in the troposphere and thus its emissions from the ocean may influence the hydroxyl radical (OH) and ozone concentrations in the marine atmospheric boundary layer that is remote from strong continental influences. 

Fig. 6.29 Idealized representation of C isotopic gradients for marine carbonate under normal photosynthesizing conditions (e.g. modern ocean), after biotic collapse (Strangelove ocean) and for dominance of microbial respiration in surface waters (after Hsii McKenzie 1990).

Here 50, denotes the observed deviation of the atmospheric O, concentration from a standard. The atmospheric tracer APO is dominated primarily by oceanic gas exchanges in addition to a relatively small contribution from fossil fuel not accounted for by the terrestrial stoichiometric factor (i.e., the fossil fuel component scaled by the factor Observations of the seasonal variation of APO in conjuction with surface-water oxy gen measurements have been used to constrain the large-scale magnitude of the air-sea gas exchange coefficient (Keeling et al, 1998) and of marine productivity (Six and Maier-Reimer, 1996 Balkan.ski et al, 1999). Mean annual gradients of APO have also been shown to provide powerful constraints on biogeochemical air-sea fluxes computed by ocean-circulation models with an embedded ocean carbon cycle (Stephens et al, 1998). 

Carbonate is an important composition of inorganic carbon in marine sediments. Up to now, the research into inorganic carbon concentrates mostly on the source, distribution, dissolution, and precipitation of carbonate in sediments. For example, in the western South China Sea, the contents of carbonate in the north and mid-southern areas are high, but low in the middle and southeast areas. The distribution characteristics are controlled by terrigenous material supply and are in close relationship with the extent of the shelf and the gradient of the slope. The contents of carbonate are highest in the area... 

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