268 
FISHERY BULLETIN OF FISH AND WILDLIFE SERVICE 
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Figure 11.—Vertical distribution of oxygen expressed in milliliters per liter (ml./L.) along sections near 100° W. (A), 110° W. (B), 120° W. (C), and 140° 
W. (D). Contour interval 0.5 ml./L. (data for A from University of California, 1956; B, C, and D modified from King et al., 1957). Depths of observa¬ 
tions are shown by dots; station numbers are given along the top of each panel. 
OCEANOGRAPHY OF EAST CENTRAL EQUATORIAL PACIFIC 
269 
at./L.), decreasing to less than 1.0 ^g. at./T.i. near 
1° S. and remaining less than this value to 8° S. 
Comparison of the phosphate concentrations in 
the mixed layer of the two sections reveals the 
association of this nonconservative property with 
the previously discussed vertical distribution of 
density (the thermocline) and zonal flow. In 
the northern portions of the sections, the low 
phosphate concentrations are in the impoverished 
waters of the Countercurrent. Near the Equator 
on 110° W., some enrichment results from up- 
welling, but the liighest values on this section, 
near 4° N., result from the very shallow thermo¬ 
cline and wind “plowing” (Sverdrup 1952) into 
the deeper, nutrient-rich waters. Near the Equa¬ 
tor on 120° W., the surface enrichment probably 
results primarily from upwelling. The northern 
transport of these waters is reflected in the higher 
phosphate values, from the Equator north to the 
latitude of the front. 
HORIZONTAL DISTRIBUTION OF PROPERTIES 
Although this section will deal primarily with 
the surface distribution of temperature, salinity, 
and phosphate, we shall, as necessary, include con¬ 
current consideration of the vertical distribution 
of the property in question. The direction of the 
flow, as determined by geostrophic calculations 
(see fig. 2) has been reproduced on the charts. 
without separating the double minima, have been 
contoured in figure 12. Values equal to or below 
0.1 ml./L. have been shaded. The values in the 
minimum near the Equator are somewhat higher 
than those to the north or to the south. 
Phosphate 
« 
The Automatic Servo-Operated Photometer 
used for the determination of inorganic phosphate 
broke down at station 8 along the 110° W. leg. 
Subsequently, samples were frozen from selected 
depths at the remainder of the stations along this 
leg, and at less frequent depth intervals (surface 
to 200 m.) along 120° W. The meridional sections 
resulting from these data are shown in figure 13. 
Along 110° W., the phosphate concentrations 
in the mixed layer were low (0.4 /xg. at./L. or less) 
betAveen the northern limit of the section (7° N.) 
and about 2° N. The values progressively in¬ 
creased to a maximum of slightly more than 1.0 
/xg. at./L. at about 3° S., then decreased to less 
than 1.0 from 5° S. to the southern limit of the 
section (8° S.). Values in the mixed layer were 
also low (0.4 /xg. at./L. or less) at the northern 
stations of the 120° W. section, but increased 
suddenly (0.4 to 1.0 /xg. at./L.) upon crossing 
the front near 4° N. The highest values in the 
surface Avaters Avere near the Equator (1.2 /xg. 
527056—60 
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