322
Chemical Oceanography, 4th Edition
addition of carbonate decreases the reduction rate. A lowering of the carbonate ion at high
pH will increase the rate of reduction. The surface waters may have higher concentrations
of Cu + that may be more toxic than Cu 2+ . These are only two possible effects on metals;
more examples will become apparent in the future since many chemical and biological
processes are affected by pH.
In summary, the expected decrease in the pH of the ocean over the next 1000 yr will affect
many chemical and biological processes in the oceans. Both good and bad effects may be
the results of the future lower pH of ocean waters. As discussed in Chapter 3, most of the
3000
7.2
7.4
7.6
pH
7.8
8.0
8.2
pCO 2
pH
8.4
2800
2600
2400
Year
2200
2000
1800
0
500
1000
1500
pCO
2 (µatm)
2000
2500
Figure 7.63
The expected pH of surface seawater over the next 1000 years. (From Millero et al., Oceanography, 22, 72–85, 2009.
With permission.)
Table 7.13
Changes in the Carbonate System Caused by Increases of pCO 2 in the
Atmosphere (S = 35, TA = 2300 μmol kg –1, and t = 25°C)
Year
pCO 2 μtm
pH
TCO 2 μmol kg –1
Ω (cal)
Ω (arg)
CO 3
2– μmol kg –1
1800
280
8.16
1906
6.76
4.46
280.9
2000
370
8.07
1968
5.77
3.81
239.9
2040
570
7.92
2057
4.39
2.89
182.3
2080
770
7.80
2113
3.55
2.34
147.5
2120
970
7.72
2152
2.99
1.97
124.1
2160
1170
7.64
2182
2.58
1.70
107.1
2200
1370
7.58
2206
2.27
1.50
94.3
2240
1570
7.53
2226
2.03
1.34
84.2
2280
1770
7.48
3343
1.83
1.21
76.10
2320
1970
7.44
2258
1.67
1.10
69.40
2360
2170
7.40
2272
1.54
1.00
63.8
2400
2370
7.36
2284
1.42
0.94
59.1