358
Chemical Oceanography, 4th Edition
Pacific. These studies showed that the ratios were consistent with the Redfield model. The
variations found with depth, latitude, and time were attributed to mixing between different water types with different preformed concentrations of O 2 , PO 4
3– , and NO 3
– . They were
unaware at the time of the conversion of NO 3
– to N 2 O in O 2 minimum zones.
Takahashi, Broecker, and Langer (1985) used GEOSEC data to examine the Redfield
ratio along isopycnal (constant- density) surfaces in the Atlantic and Indian Oceans. Their
values corrected for mixing are given in Table 8.9. The authors attempted to correct the
CO 2 values for the dissolution of CaCO 3 . The mean values of P:N:C:O 2 were found to be
1:17:100:165 at σ T = 27.0 and 1:17:92:178 at σ T = 27.2. The small differences between horizons
cannot be explained. They suggest values of 1:16:103:172. If the C value is assumed to be
represented by the oxygen utilization minus the O 2 used for oxidation of NH 3 with 2 moles
of O 2 , a ratio of 1:16:140:172 is obtained. The P:O 2 ratio lies between 1:103 and 1:140. This difference may be due to the increase of CO 2 caused by the anthropogenic CO 2 or an excess
N/P
0
5
10
15
20
25
30
Depth (m)
0
200
400
600
800
1000
1200
Hawaii
Bermuda
Figure 8.20
The nitrogen- to- phosphate molar ratio at the Bermuda and Hawaii time series stations.
Table 8.9
Molecular Ratios of P, N, C, O 2 , and CaCO 3 Changes in the Atlantic
and Indian Oceans
Location
Surface P
N
CO 2
(O 2 -2N)
O 2
CaCO 3
North Atlantic
27
1
17.6 ± 0.6
97 ± 9
130 ± 6
165 ± 7
15 ± 4
27.2
1
16.8 ± 0.5
88 ± 6
139 ± 6
173 ± 6
8 ± 3
South Atlantic
27
1
16.7 ± 0.7
102 ± 7
131 ± 6
165 ± 6
8 ± 2
27.2
1
16.7 ± 1.2
95 ± 10
150 ± 2
182 ± 9
8 ± 4
Mean Atlantic
1
17 ± 0.4
96 ± 6
138 ± 9
171 ± 8
10 ± 4
South Indian
27
1
15.2 ± 0.6
112 ± 6
138 ± 7
169 ± 8
15 ± 4
27.2
1
14.5 ± 0.5
125 ± 7
145 ± 5
174 ± 6
19 ± 6
Mean Indian
1
14.9 ± 0.4
119 ± 5
142 ± 5
172 ± 5
17 ± 4
Overall mean
1
16.3 ± 1.1
103 ± 14
140 ± 8
172 ± 7
12 ± 5
Chemical Oceanography, 4th Edition
Pacific. These studies showed that the ratios were consistent with the Redfield model. The
variations found with depth, latitude, and time were attributed to mixing between different water types with different preformed concentrations of O 2 , PO 4
3– , and NO 3
– . They were
unaware at the time of the conversion of NO 3
– to N 2 O in O 2 minimum zones.
Takahashi, Broecker, and Langer (1985) used GEOSEC data to examine the Redfield
ratio along isopycnal (constant- density) surfaces in the Atlantic and Indian Oceans. Their
values corrected for mixing are given in Table 8.9. The authors attempted to correct the
CO 2 values for the dissolution of CaCO 3 . The mean values of P:N:C:O 2 were found to be
1:17:100:165 at σ T = 27.0 and 1:17:92:178 at σ T = 27.2. The small differences between horizons
cannot be explained. They suggest values of 1:16:103:172. If the C value is assumed to be
represented by the oxygen utilization minus the O 2 used for oxidation of NH 3 with 2 moles
of O 2 , a ratio of 1:16:140:172 is obtained. The P:O 2 ratio lies between 1:103 and 1:140. This difference may be due to the increase of CO 2 caused by the anthropogenic CO 2 or an excess
N/P
0
5
10
15
20
25
30
Depth (m)
0
200
400
600
800
1000
1200
Hawaii
Bermuda
Figure 8.20
The nitrogen- to- phosphate molar ratio at the Bermuda and Hawaii time series stations.
Table 8.9
Molecular Ratios of P, N, C, O 2 , and CaCO 3 Changes in the Atlantic
and Indian Oceans
Location
Surface P
N
CO 2
(O 2 -2N)
O 2
CaCO 3
North Atlantic
27
1
17.6 ± 0.6
97 ± 9
130 ± 6
165 ± 7
15 ± 4
27.2
1
16.8 ± 0.5
88 ± 6
139 ± 6
173 ± 6
8 ± 3
South Atlantic
27
1
16.7 ± 0.7
102 ± 7
131 ± 6
165 ± 6
8 ± 2
27.2
1
16.7 ± 1.2
95 ± 10
150 ± 2
182 ± 9
8 ± 4
Mean Atlantic
1
17 ± 0.4
96 ± 6
138 ± 9
171 ± 8
10 ± 4
South Indian
27
1
15.2 ± 0.6
112 ± 6
138 ± 7
169 ± 8
15 ± 4
27.2
1
14.5 ± 0.5
125 ± 7
145 ± 5
174 ± 6
19 ± 6
Mean Indian
1
14.9 ± 0.4
119 ± 5
142 ± 5
172 ± 5
17 ± 4
Overall mean
1
16.3 ± 1.1
103 ± 14
140 ± 8
172 ± 7
12 ± 5