SALINITY IN (%o) 



250 



200 



-78KM.- 



Figure 20. — Salinity profile and salinity-depth curves for the second (E) triplet of hydrocasts at front 5 (23 April 

 1961). The dashed line on the profile is the corresponding 16.5° C. isotherm (figs. 18 and 19). Note the salin- 

 ity maximum (>34. 80°,,,) of equatorial Pacific water at about 150 m. c = cool side; m = middle; w = warm side; 

 • = Nansen bottle depths in profile. 



similar to each other than are those of the B 

 series profile. Immediately below the nitrite 

 maximum, in both series of data, the water 

 has a low oxygen content which is inversely 

 related to the value of the nitrite maximum at 

 each station (e.g., at station 5E2 the nitrite 

 maximum is low while the oxygen content is 

 relatively high; compare figs. 26 and 27 with 

 28). 



There is a marked nitrite maximum at about 

 250 m. on the cool side. Such a maximum is 

 found in samples taken between lat. 21° N.and 

 8° N. (Brandhorst, 1959). It is associated with 

 the oxygen minimum of the eastern tropical 

 Pacific waters (Brandhorst, 1959) and to some 

 extent with the salinity maximum of those 

 waters, as Brandhorst's appended data show 

 but to which he does not draw attention. It is 

 surprising here, however, that this deep maxi- 

 mum is found only on the cool side of the front 



which would be the side less expected to have 

 it. The maximum does not occur in the E series 

 profile, and the possibility that the observation 

 is due to faulty measurement cannot be ruled 

 out entirely. Being below the frontal zone, the 

 deep maximum is not of direct concern here. 

 The nitrate profile of the B series casts 

 (fig. 29) shows that only at the cool station 

 were there considerable changes at depth. 

 The information available does not provide any- 

 obvious explanation of these changes, and the 

 low value at 125 m. may be erroneous. The 

 marked gradient between about 40 and 50 m. 

 on the cool side corresponds fairly well with 

 those of temperature, thermosteric anomaly, 

 and oxygen (figs. 17, 21, and 26). Below 40 m. 

 on the cool side the oxygen content decreases 

 rapidly as the nitrate increases rapidly; how- 

 ever, the relation is not so clear-cut on the 

 warm side. 



27 



