286
Chemical Oceanography, 4th Edition
Atlantic and 1200 μatm in the Pacific) at 1 km because of the oxidation of plant material.
The higher values at 1 km in the Pacific are due to the higher productivity of the surface waters, resulting in the production of more organic carbon. The deep- water values
in the Pacific are higher than in the Atlantic because of the fact that the waters are older
and have accumulated more CO 2 from the oxidation of organic carbon as the waters make
the trip from the North Atlantic to the North Pacific (600 yr). The deep waters originally
formed at the surface have lower pCO 2 than the values at the oxygen minimum.
7.5.2 pH
The pH of most surface waters in equilibrium with the atmosphere is 8.2 ± 0.1. Recent
measurements of pH in the surface waters of the Atlantic and Pacific Oceans are shown in
Figure 7.19 and Figure 7.20, respectively. The gross trends in pH are those expected from
the surface pCO 2 (the higher the pCO 2 , the lower the pH and vice versa). The values are
lower in upwelling waters in the equatorial regions and are proportional to temperature.
In closed or small bodies of water, the pH can show diurnal variations and cycle between
8.2 and 8.9. The decrease occurs in the evening because of the respiration of organisms,
and the increase occurs in the afternoon because of photosynthesis. Changes in the pH
with depth in the Atlantic and Pacific Oceans are shown in Figure 7.21. Although it is difficult to see in this figure, the pH goes through a maximum in surface waters because of
photosynthesis. The loss of CO 2 increases the pH. The pH then decreases because of the
oxidation of plant material and goes through a minimum at about 1 km. This minimum
coincides with the O 2 minimum and the maximum in pCO 2 .
190
275
300
Seawater pCO 2 (µatm) at SST
Climatological pCO 2 in Surface Water for February 1995
325
350
375
400
425
480
Figure 7.16
The global distribution of pCO 2 (μatm) for surface waters of the world oceans. (From Takahashi, T., et al., Net
air–sea CO 2 flux over global oceans: an improved estimate based on sea–air pCO 2 differences, in Proceedings of
2nd International Symposium on CO 2 in the Oceans, CGER-1037-99, CGER/ NIES, Tsukuba, Japan, 1999, pp. 9–15.
With permission.)
Chemical Oceanography, 4th Edition
Atlantic and 1200 μatm in the Pacific) at 1 km because of the oxidation of plant material.
The higher values at 1 km in the Pacific are due to the higher productivity of the surface waters, resulting in the production of more organic carbon. The deep- water values
in the Pacific are higher than in the Atlantic because of the fact that the waters are older
and have accumulated more CO 2 from the oxidation of organic carbon as the waters make
the trip from the North Atlantic to the North Pacific (600 yr). The deep waters originally
formed at the surface have lower pCO 2 than the values at the oxygen minimum.
7.5.2 pH
The pH of most surface waters in equilibrium with the atmosphere is 8.2 ± 0.1. Recent
measurements of pH in the surface waters of the Atlantic and Pacific Oceans are shown in
Figure 7.19 and Figure 7.20, respectively. The gross trends in pH are those expected from
the surface pCO 2 (the higher the pCO 2 , the lower the pH and vice versa). The values are
lower in upwelling waters in the equatorial regions and are proportional to temperature.
In closed or small bodies of water, the pH can show diurnal variations and cycle between
8.2 and 8.9. The decrease occurs in the evening because of the respiration of organisms,
and the increase occurs in the afternoon because of photosynthesis. Changes in the pH
with depth in the Atlantic and Pacific Oceans are shown in Figure 7.21. Although it is difficult to see in this figure, the pH goes through a maximum in surface waters because of
photosynthesis. The loss of CO 2 increases the pH. The pH then decreases because of the
oxidation of plant material and goes through a minimum at about 1 km. This minimum
coincides with the O 2 minimum and the maximum in pCO 2 .
190
275
300
Seawater pCO 2 (µatm) at SST
Climatological pCO 2 in Surface Water for February 1995
325
350
375
400
425
480
Figure 7.16
The global distribution of pCO 2 (μatm) for surface waters of the world oceans. (From Takahashi, T., et al., Net
air–sea CO 2 flux over global oceans: an improved estimate based on sea–air pCO 2 differences, in Proceedings of
2nd International Symposium on CO 2 in the Oceans, CGER-1037-99, CGER/ NIES, Tsukuba, Japan, 1999, pp. 9–15.
With permission.)