Carbon reservoirs oceans

In situations where Tobs is comparable in magnitude to tq, a more complex relation prevails between Q, S, and M. Atmospheric CO2 falls in this last category although its turnover time (3 years, cf. Fig. 4-3) is much shorter than Tobs (about 300 years). This is because the atmospheric CO2 reservoir is closely coupled to the carbon reservoir in the biota and in the surface layer of the oceans (Section 4.3). The effective turnover time of the combined system is actually several hundred years (Rodhe and Bjdrk-strom, 1979). 

The content of the material in a carbon reservoir is a measure of that reservoir s direct or indirect exchange rate with the atmosphere, although variations in solar also create variations in atmospheric content activity (Stuiver and Quay, 1980, 1981). Geologically important reservoirs (i.e., carbonate rocks and fossil carbon) contain no radiocarbon because the turnover times of these reservoirs are much longer than the isotope s half-life. The distribution of is used in studies of ocean circulation, soil sciences, and studies of the terrestrial biosphere. 

The freshwater cycle is an important link in the carbon cycle as an agent of erosion and as a necessary condition for terrestrial life. Although the amount of carbon stored in freshwater systems is insignificant as a carbon reservoir (De Vooys, 1979 Kempe, 1979a), about 90% of the material transported from land to oceans is carried by streams and rivers. 

The crust is the largest carbon reservoir in the crustal-ocean-atmosphere factory (8 x 10 Pg C including the sediments). Most of this carbon is in the form of inorganic minerals, predominantly limestone, with the rest being organic matter, predominantly contained in shale and secondarily in fossil fuel deposits (coal, oil, and natural gas). The oceanic reservoir (4 X lO" Pg C) and the terrestrial reservoir (2 to 3 x 10 Pg C) are both far smaller than the crustal reservoir. The smallest reservoir is found in the atmospheric, primarily as CO2 (preindustrial 6 x 10 Pg C, now 8 x 10 Pg C and rising). The flux estimates in Figure 25.1 have been constrained by an assumption that the preindustrial atmospheric and oceanic reservoirs were in steady state over intermediate time scales (millennia). 

In these models the increase in the number of factors considered is clearly observed, as is the respective increasing adequacy that accompanies them. One of the first and sufficiently complete models of the global C02 cycle is the model proposed by Bjorkstrom (1979) which takes into account the dynamic interaction between carbon reservoirs in the biosphere and fluxes between them. For the first time, a unit for the World Ocean was realistically represented. In this unit the ocean is... 

From Figure 9.1, it can be seen that the major form of carbon in the atmosphere is C02(g), constituting over 99% of atmospheric carbon. Carbon dioxide makes up 0.035% by volume of atmospheric gases, or 350 ixatm = 350 ppmv. The atmosphere has a mass of CO2 that is only 2% of the mass of total inorganic carbon in the ocean, and both of these carbon masses are small compared to the mass of carbon tied up in sediments and sedimentary rocks. Therefore, small changes in carbon masses in the ocean and sediment reservoirs can substantially alter the CO2 concentration of the atmosphere. Furthermore, there is presently 3 to 4 times more carbon stored on land in living plants and humus than resides in the atmosphere. A decrease in the size of the terrestrial organic carbon reservoir of only 0.1% y-1 would be equivalent to an increase in the annual respiration and decay carbon flux to the atmosphere of nearly 4%. If this carbon were stored in the atmosphere, atmospheric CO2 would increase by 0.4%, or about 1 ppmv y-l. The... 

Variability in the Amount of Carbon in Reservoirs. In addition to variations in the production and distribution of radiocarbon over time and within portions of various carbon reservoirs, variations may result in situations where carbon not in equilibrium with the contemporary standard values is added or removed from any reservoir. Two instances of this are well documented since they occurred within the last century as a result of human intervention. The first is known as the industrial or Suess effect and is caused by the combustion of fossil fuels beginning about 1890, resulting in a depletion of atmospheric activities by about 3% (76). A more recent occurrence has been called the atomic bomb or Libby effect. The detonation of nuclear devices in the atmosphere beginning in 1945 produced large amounts of artificial increasing the radiocarbon concentrations in the atmosphere by more than 100% in the Northern Hemisphere (77). Because of equilibration with the oceans, the levels have been diminishing steadily since the atmospheric testing was terminated by the major nuclear powers except France and the People s Repub-... 

Recent pelagic sediments containing over 30% calcium carbonate, by dry weight, cover a quarter of the surface of the earth (see Figure 1). These sediments make up a vast and chemically reactive carbonate reservoir which has a major influence on the chemistry of the oceans and atmosphere. In order to have a predictive understanding of the natural carbon dioxide system and the influence of man on it, the chemical dynamics of calcium carbonate deposition in the deep ocean basins must be known in detail. 

The resulting enters the carbon reservoir on the Earth s surface, mixing with stable as dissolved in the oceans, as in the atmosphere, and in the... 

On geological time scales, CO2 cycles between rocks, often by way of the ocean and atmosphere. The rock reservoirs include the mantle, continental carbonates, carbon in reduced form mostly in continental shales, and carbon (mostly carbonate) in or on the sea floor. The small volatile reservoir (ocean plus atmosphere) cycles through carbonate rock in a hundred thousand to a million years. Over longer periods free CO2 is dynamically controlled by processes that form carbonates at low temperatures and processes that decompose carbonates at high temperatures by (Urey) reactions of the form... 

The rate of global production of bicarbonate by weathering can be determined because we loiow approximately the flow of HCO J in the world s major rivers. This represents a drain of the CO2 of the atmosphere, which must be balanced by resupply to maintain a steady One is tempted to estimate the vulnerability of atmospheric/co to the imbalance between the atmospheric CO2 drain by weathering and resupply by CaCOs precipitation by focusing on the CO2 fluxes from and to the atmosphere. This, however, would be incorrect because the ocean and atmosphere carbon reservoirs are approximately in chemical equilibrium on time scales greater than the circulation of the ocean (see Chapter 11). In order to emphasize the severity of the HCOs imbalance estimated in Fig. 2.4 one should focus on the fluxes of DlC and alkalinity between the land and ocean. Because we have not yet discussed alkalinity and DIC relationships (Chapter 4) a simple approximation can be made by considering the fluxes of bicarbonate and calcium. 

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