lesser degree at station 11; in contrast the 

 oxygen isopleths are raised at stations 10 and 

 12 where there are high-salinity nodes. These 

 relationships are discussed further under 

 oxygen distribution. 



In the next profile south, stations 23 through 

 37 (fig. 22), the complications have largely 

 disappeared. The deep-salinity minimum and 

 the maximum above it are present, the maxi- 

 mum again represented by isohalines of 34.80 

 p.p.t. This value of the salinity maximum is 

 found over much of the eastern tropical Pacific 

 (Wyrtki, 1967; Bennett, 1963). The node of water 

 of salinity about 34.80 p.p.t. at 100 m. be- 

 tween stations 29 and 31 is probably not part 

 of the maximum because it is associated with 

 isanosteres near 240 cl./ton rather than 130 

 to 180 cl./ton. Presumably this particular 

 node is more correctly associated with the 

 maximum due to Gulf Surface Water, at about 

 50 m. between stations 35 and 37. Such a 

 maximum was found off Cape San Lucas at the 

 eastern end of line 153 (fig. 19), also about 

 the 240 cl./ton isanostere. The high surface 

 salinities due to Gulf Surface Water, with 

 which the isohalines of the salinity maxinnum 

 usually connect in the Gulf mouth, are asso- 

 ciated with isanosteres between 360 and 460 

 cl./ton. The relatively high surface salinities 

 at the western end of the profile persist and 

 the shallow salinity minimum of the California 

 Current Surface Water is definite, although 

 now somewhat thinner. This minimum extends 

 its influence to the coast off Mazatlan, more 

 or less following the thermocline and appear- 

 ing to penetrate the high- salinity Gulf Water 

 in the upper 100 m.; hence there is saltier 

 water above and below the California Water. 

 There is some possibility that the low-salinity 

 water (about 34.50 p.p.t.) at about 20 m. 

 at the easternmost end of this profile (station 

 37) was caused by river runoff in the region 

 around Mazatlan. Roden and Groves (1959) 

 suggested this possibility; however, the rainy 

 season is in late summer and autumn. The 

 extension of the low-salinity water from the 



west corresponds to one of relatively high 

 oxygen content. 



Farther south, between stations 40 and 48, 

 the high salinity of the Gulf Surface Water 

 is evident on the eastern side and extends its 

 influence to the west, especially at the sur- 

 face (fig. 23). The shallow minimum of the 

 California Current Surface Water is much more 

 restricted in this profile than in the previous 

 one, but it still extends, nnuch attenuated, 

 almost to the coast on the eastern side. 

 The maximum of the Subtropical Water is, 

 as before, marked by the 34.80 p.p.t. isohaline 

 which also circumscribes some Gulf Surface 

 Water, in a layer at about 80 m. between 

 stations 40 and 44; this maximum underlies the 

 low- salinity extension from the west. 



The southernmost profile (fig. 24) is like 

 the one just to the north, but the shallow 

 minimum is more restricted to the western 

 side, though again it still extends its effects 

 to the coast. In all these salinity profiles the 

 shallow minimum, originating in California 

 Current Surface Water, appears to compete 

 with high- salinity Gulf Surface Water for 

 density surfaces along which to spread, be- 

 cause this high-salinity water is found above 

 and below the lower salinity water. The salinity 

 minimum can be most liberally proscribed by 

 the 34.60 p.p.t. isohaline, because no water 

 in the upper 100 m. off western Lower Cali- 

 fornia has a salinity exceeding 34.60 p.p.t. 

 (except as noted at station 153.16), and no 

 water in the immediate vicinity to the south 

 or east has a salinity in the upper 100 m. of 

 less than 34.60 p.p.t. (except for the possibility 

 of river runoff already noted). 



Along the southernmost line the salinity 

 maximum is described entirely by water of 

 > 34.80 p.p.t. In this profile as well as in the 

 others, the top of the oxygen minimum (dashed 

 contour) is associated with the salinity maxi- 

 mum. Between stations 50 and 56 the deep 

 salinity minimum is still present and is of 

 nearly uniform salinity (< 34.60 p.p.t.); this 

 agrees broadly with descriptions of this feature 

 given by Bennett (1963) and Wyrtki (1967). 



25 



