295
The Carbonate System
carbon dioxide in the atmosphere to the fractional increase of the total carbon dioxide in the
ocean. The increase in the TCO 2 near the equator is related to the Revelle factor:
R = (ΔpCO 2 /pCO 2 )/(ΔTCO 2 /TCO 2 )
(7.125)
This value is about 14 for cold waters and 8 for warmer waters (the average is about 10). Thus,
a 10% change in pCO 2 results in only a 1% change in TCO 2 . This factor is important when
considering the effect that increases of CO 2 in the atmosphere have on the carbonate system.
Sections of TCO 2 in the Atlantic and Pacific are shown in Figure  7.34. The values in
the deep waters increase from the North Atlantic (2180 μmol kg –1 ) to the North Pacific
(2380 μmol kg –1 ) because of the oxidation of organic carbon and dissolution of CaCO 3 .
7.6 CaCO 3 Dissolution in Seawater
The precipitation or formation of solid CaCO 3 in surface seawaters and the dissolution
of solid CaCO 3 in deep waters is very important in transferring CO 2 from surface waters
to deep waters. CaCO 3 (s) is also present in pelagic sediments of the world oceans (see
Figure 7.35).
Latitude
Latitude
–50 –40 –30 –20 –10 0 10 20 30 40 50 60 70
TCO
2 (µmol kg
–1
)
1850
1900
1950
2000
2050
2100
2150
Atlantic
Pacific
–70 –60 –50 –40 –30 –20 –10
0
10 20 30
TCO
2 (µmol kg
–1
)
1850
1900
1950
2000
2050
2100
2150
2200
Figure 7.29
Surface values of the total carbon dioxide (TCO 2 ) in the Atlantic and Pacific Oceans.