The Carbon Cycle - Introduction to Carbon Capture and Sequestration - page 103

Figure 3.1.1 Part of the carbon cycle
A simplifi ed representation of the contemporary global carbon cycle. Figure from the US
Department of Energy's Offi ce of Science Genomic Science Program [3.1].
minerals. These are partly found in the oceans, but the vast majority are
in sediments and crust.
Our next step is to consider the various mechanisms that allow carbon
to exchange between these different reservoirs. We fi rst apply our chemical
intuition. Chemists understand that in order to keep the concentration of a
chemical nearly constant, they use a buffer. The most important property of
buffers is that their concentration is much larger than that of the chemicals
they seek to control. If we would like to buffer the CO 2 concentration in the
atmosphere, we therefore need a large reservoir of carbon. Figure 3.1.2
shows that terrestrial carbon and carbon in the surface of the ocean exist in
amounts similar to the total amount of carbon in the atmosphere. And so these
reservoirs do not act as a buffer. The carbon reservoirs in the deep ocean and
in sediments and crust are, however, suffi ciently large to act as buffers.
The next step in our system analysis is to describe the interactions
between the different reservoirs. This will be the topic of the next section.