Carbon cycles, global ocean

Examples of typical impulse-response functions are shown in Figs. 4 and 5 (adopted from Hooss et al., 2001). The net impulse-response function of the coupled carbon-cycle/physical ocean-atmosphere system is given by a convolution (cf. Hasselmann et al., 1997) of the linear impulse-response function for the carbon cycle alone (representing the atmospheric CO2 response to a S-function CO2 input) and the response function of the physical ocean-atmosphere system (representing the response of the physical system variables to a step-function increase in the CO2 concentration). Figure 4 shows the response function R,. for the carbon cycle and the response functions Rj and R, for the global mean temperature and mean sea-level rise, respectively, for the physical climate system. The resulting net response functions for R,., R(2)> and R(,) for the coupled carbon-cycle/physical ocean-atmosphere system are shown in Fig. 5. 

Figure 1. Changes in global climate due to increased atmospheric CO2 will alter carbon cycle processes in land, continent margins, and oceans, which will in turn effect the atmospheric C02concentration. Processes that may have effects large enough to Eilter future projections of atmospheric CO2 are listed under their geographic region.

The most common way in which the global carbon budget is calculated and analyzed is through simple diagrammatical or mathematical models. Diagrammatical models usually indicate sizes of reservoirs and fluxes (Figure 1). Most mathematical models use computers to simulate carbon flux between terrestrial ecosystems and the atmosphere, and between oceans and the atmosphere. Existing carbon cycle models are simple, in part, because few parameters can be estimated reliably. 

Another model, first introduced by Moore, et al. (2i), was used to examine the role of terrestrial vegetation and the global carbon cycle, but did not include an ocean component. This model depended on estimates of carbon pool size and rates of CO2 uptake and release. This model has been used to project the effect of forest clearing and land-use change on the global carbon cycle (22, 23, 24). 

Bjorkstrom, A. 1979. A model of CO2 interaction between atmosphere,oceans, and land biota. In The Global Carbon Cycle, Bolin, B. Degens, E. T. Kempe, S. Ketner, P., Eds. SCOPE 13 J Wiley Sons New York, NY, 1979 pp 403-457. 

Budgets and cycles can be considered on very different spatial scales. In this book we concentrate on global, hemispheric and regional scales. The choice of a suitable scale (i.e. the size of the reservoirs), is determined by the goals of the analysis as well as by the homogeneity of the spatial distribution. For example, in carbon cycle models it is reasonable to consider the atmosphere as one reservoir (the concentration of CO2 in the atmosphere is fairly uniform). On the other hand, oceanic carbon content and carbon exchange processes exhibit large spatial variations and it is reasonable to separate the... 

Rainwater and snowmelt water are primary factors determining the very nature of the terrestrial carbon cycle, with photosynthesis acting as the primary exchange mechanism from the atmosphere. Bicarbonate is the most prevalent ion in natural surface waters (rivers and lakes), which are extremely important in the carbon cycle, accoxmting for 90% of the carbon flux between the land surface and oceans (Holmen, Chapter 11). In addition, bicarbonate is a major component of soil water and a contributor to its natural acid-base balance. The carbonate equilibrium controls the pH of most natural waters, and high concentrations of bicarbonate provide a pH buffer in many systems. Other acid-base reactions (discussed in Chapter 16), particularly in the atmosphere, also influence pH (in both natural and polluted systems) but are generally less important than the carbonate system on a global basis. 

Baes, C. F., Bjdrkstrom, A. and MuIhoUand, P. J. (1985). Uptake of carbon dioxide by the oceans. In "Atmospheric Carbon Dioxide and the Global Carbon Cycle" (J. R. Trabalka, ed.). Report DOE/ ER-0239, US Department of Energy, Office of Energy Research, Washington, DC. 

Fig. 11-18 A four-box model of the global carbon cycle. Reservoir inventories are given in moles and fluxes in mol/yr. The turnover time of CO2 in each reservoir with respect to the outgoing flux is shown in brackets. (Reprinted with permission from L. Machta, The role of the oceans and biosphere in the carbon dioxide cycle, in D. Dryssen and D. Jagner (1972). "The Changing Chemistry of the Oceans," pp. 121-146, John Wiley.)...

Bjdrkstrom, A. (1979). A model of CO2 interaction between atmosphere, oceans, and land biota. In "The Global Carbon Cycle" (B. Bolin, E. T. Degens, S. Kempe, and P. Ketner, eds), pp. 403-457. Wiley, New York. 

Siegenthaler, U. and Joos, F. (1992). Use of a simple model for studying oceanic tracer distributions and the global carbon cycle, Tellus 44B, 186-207. 

To solve this problem, we need to make computer calculations on the long-term global carbon cycle including the effect of terrestrial biota, ocean circulation pattern, and metamorphic activities which are not included in Kashiwagi et al. (2000) s computation. 

A major opportunity to test the use of " Th as a proxy for POC flux arose with the Joint Global Ocean Flux Study (JGOFS). JGOFS had as a central goal a better understanding of the ocean carbon cycle, including the flux of POC leaving the euphotic zone. Process studies were carried out in the Atlantic Ocean, Pacific Ocean, Arabian Sea and Southern Ocean. " Th profiles were obtained as a part of each process study. 

Guilderson, T.P., K. Caldeira, and P.B. Duffy. 2000. Radiocarbon as a diagnostic tracer in ocean and carbon cycle modeling. Global Biogeochemical Cycles 14(3) 887-902. 

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