287
The Carbonate System
The pH increase in deep waters is due to the dissolution of CaCO 3 . The pH of deep
waters can be as low as 7.5 near 1000 m. In very deep waters, the pH can go through a
maximum because of the effect of pressure on the ionization of carbonic acid. Park (1969)
has used the Redfield et al. (1963) model to calculate the pH as a function of depth. He
attributed the changes to two factors:
ΔpH = ΔpH(a) + ΔpH(b)
(7.124)
1980
1970
TCO
2 (µM)
del C13 (ppm)
1960
1950
Bermuda
1940
1930
1920
1.0
1.1
1984
1988
1992
1996
2000
1.2
1.3
1.4
1.5
1.6
1.7
2300
2290
2280
2270
NTA (µM)
400
380
360
340
320
300
pCO
2 (ppm)
2000
1990
TCO
2 (µM)
del C13 (ppm)
1980
1970
Hawaii
1960
1950
1940
1.0
1.1
1984
1988
1992
1996
2000
1.2
1.3
1.4
1.5
1.6
1.7
1.8
2320
2310
2300
2290
NTA (µM)
400
380
360
340
320
300
pCO
2 (ppm)
Figure 7.17
The variations of pCO 2 , δC 13 , TA, and TCO 2 at the Bermuda and Hawaii time series stations.