263
The Carbonate System
with seawater. Although this process is slow, Sarmiento’s calculations indicate that the
addition of 1095 molecules of CO 2 to the atmosphere will decrease to 15 molecules after
1000 yr (see Table 7.2). Most of the added CO 2 (985 molecules) will end up as part of the
inorganic pool as bicarbonate and carbonate ions.
Before we examine the distribution of CO 2 in the oceans, the concepts needed to understand the carbonate system in the oceans are discussed.
Table 7.1
Budget for the Global CO 2 System (1980–1989)
Average Perturbation
(10 15 g carbon yr –1 )
Sources
Fossil fuel combustion
5.4 ± 0.5
Deforestation
1.6 ± 1.0
Total
7.0 ± 1.2
Sinks
Atmosphere
3.4 ± 0.2
Oceans (models)
2.0 ± 0.8
Total
5.4 ± 0.8
Unaccounted for sinks
1.6 ± 1.4
13 C /12 C
–0.5
0.0
0.5
1.0
1.5
2.0
Depth (m)
0
500
1000
1500
2000
1970
1990
Oceanic CO 2 Uptake
2.1 GtC yr
–1
25–35 m yr
–1
Penetration Rate
Figure 7.6
The changes in the ratio of 13 C/ 12 C as a function of depth. (Modified from Quay, P.D., Tilbrook, B., and Wong,
C.S., Science, 256, 74, 1992.)