Biosphere-atmosphere exchange processes

There are different time scales associated with the various emissions and uptake processes. Two terms that are frequently used are turnover time and response or adjustment) time. The turnover time is defined as the ratio of the mass of the gas in the atmosphere to its total rate of removal from the atmosphere. The response or adjustment time, on the other hand, is the decay time for a compound emitted into the atmosphere as an instantaneous pulse. If the removal can be described as a first-order process, i.e., the rate of removal is proportional to the concentration and the constant of proportionality remains the same, the turnover and the response times are approximately equal. However, this is not the case if the parameter relating the removal rate and the concentration is not constant. They are also not equal if the gas exchanges between several different reservoirs, as is the case for C02. For example, the turnover time for C02 in the atmosphere is about 4 years because of the rapid uptake by the oceans and terrestrial biosphere, but the response time is about 100 years because of the time it takes for C02 in the ocean surface layer to be taken up into the deep ocean. A pulse of C02 emitted into the atmosphere is expected to decay more rapidly over the first decade or so and then more gradually over the next century. 

An important stage in understanding the processes of C02 exchange between biospheric reservoirs is study of the laws of the development of various ecosystems in pre-industrial epochs, when there was little human involvement. Natural carbon fluxes between the atmosphere, oceans, land ecosystems, and inland water bodies... 

The functioning of the atmosphere-land border in the process of C02 exchange includes other fluxes H9, Hf4, and Hf5, which play an important role in the carbon balance of the biosphere. Bjorkstrom (1979) used the following relationships to describe these fluxes in his model of the biospheric balance of C02 ... 

The free 14C atoms formed in the atmosphere become oxidized and form 14C02 which is rapidly mixed throughout the atmosphere (Libby, 1952). This 14C then becomes incorporated into other reservoirs such as the biosphere, as plants fix carbon during the process of photosynthesis the exchange between the atmosphere and the surface ocean is estimated to take approximately 5 y (Broecker and Peng, 1982). 

Atmospheric CO2 provides a link between biological, physical, and anthropogenic processes. Carbon is exchanged between atmosphere, the ocean, the terrestrial biosphere, and, more slowly, with sediments and sedimentary rocks. The faster components of the cycle are shown in Figure 10. 

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