THE KINDS OF WATER IN THE MOUTH 

 OF THE GULF 



Roden and Groves (1959) stated that the 

 entrance to the Gulf of California has three 

 kinds of water: Gulf Water, California Current 

 Water, and Eastern Tropical (or equatorial) 

 Pacific Water. They did not thoroughly define 

 the three types. Wyrtki (1967) defined the 

 water masses of the eastern Pacific in ways 

 with which my results can be compared. 



Figure 2 shows T-S- 8 -j.^ curves for some of 

 the CalCOFI (cruise 6004-B) stations online 

 120, off Point San Eugenio (28° N., 115° W.), 

 and on line 143, off Magdalena Bay (fig. 1). 

 Figure 3 shows similar curves for stations 

 farther south, on line 153 of the CalCOFI 

 pattern and for TO-60-1 stations west of 

 Cape San Lucas. 



Figures 4 and 5 show T-S-8 .j. curves for TO- 

 60-1 stations in the southern and northeastern 

 parts of the Gulf entrance. 



Where there are data from depths greater 

 than about 700 m. all these curves demon- 

 strate the presence of the oceanwide Interme- 

 diate Water (Sverdrup, Johnson, and Fleming, 

 1942) in the shape of a salinity minimum for 

 which Wyrtki (1967, fig. 4) suggested the fol- 

 lowing roughlimits: T: 4.5to6.4 C; S: 34.2 

 to 34.6 p.p.t. (parts per thousand). 



Wyrtki (1967, fig. 4) defined the average 

 T-S relationship of equatorial subsurface water 

 and its immediate derivative. Subtropical Sub- 

 surface Water, by the line between the co- 

 ordinates 6.8° C, 34.5 p.p.t. and 17.0° C, 

 35.2 p.p.t. All the T-S- 8 ^ curves except those 

 from lines 120 and 143 (fig. 2), show a sig- 

 nificant agreement with this line within the 

 range of salinities observed. Since this water 

 flows beneath water of lower salinity, ex- 

 cept in the Gulf of California, it gives rise 

 to a salinity maximum of about 34.80 p.p.t., 

 which is obscured in the Gulf (see below). 

 This maximum, for our data, comprises water 

 of temperatures between about 10 and 13° C. 

 and thermosteric anomalies between about 130 

 and 180 cl./ton. It is recognizable in the 



^ j-pis the thermosteric anomaly, defined by Mont- 

 gomery and Wooster (1954), and measured in units of 10-^ 

 centiliters/metric ton but given for convenience as cl./ 

 metric ton. 



curves from lines 120 and 143 (fig. 2) in a 

 similar density range, but at lower salinity. 



Subtropical Surface Water is warm and of 

 fairly high salinity (>34.5 p.p.t. in the North 

 Pacific, according to Wyrtki, 1967). This 

 water, probably together with some California 

 Current Surface Water, supplies the Gulf of 

 California, where its salinity is raised so much 

 by evaporation ( > 35.0 p.p.t.) that the salinity 

 maximum mentioned above is obscured (fig. 5). 

 This high-salinity derivative. Gulf Surface 

 Water, flows out of the Gulf and separates 

 two kinds of water of lower salinity- -California 

 Current Surface Water to the north, and 

 unmodified Subtropical Surface Water and 

 Tropical Surface Water (Wyrtki, 1967) to 

 the south (see Sund, 1961, for T-S curves; 

 and Bennett, 1966, for surface salinity charts). 

 Gulf Surface Water also flows northward off 

 western Lower California late in the year 

 (Bennett, 1963; Griffiths, 1965; Wyrtki, 1967). 

 By mixing with the California Current Sur- 

 face Water, which is also subjected to rela- 

 tively high insolation and consequent salinity 

 increase at the surface, at this latitude, the 

 Gulf Surface Water helps to form salinities 

 at the surface that are greater than those 

 immediately below the surface where, conse- 

 quently, a salinity minimum forms (compare 

 figs. 2 and 3). This minimum marks the 

 presence of California Current Surface Water, 

 albeit in an ever more modified form with 

 decreasing latitude. Below the minimum is 

 a transition of the T-S- St relationship to that 

 of the Subtropical Subsurface Water. 



From this discussion it is clear that the 

 three kinds of water alluded to by Roden and 

 Groves (1959) and by Griffiths (1965) are 

 composite when their data are reviewed in 

 relation to the terms set out by Wyrtki (1967). 

 This is not to say that these authors were 

 unaware of the composite nature of the water 

 types they discussed. 



Table 1 shows the composition of the 

 three kinds of water; only depths above the 

 60 cl./ton density surface are considered, 

 because few observations were made deeper 

 than this. The ranges in thermosteric anom- 

 aly are approximate, and I attempted to 

 take into account vertical transitions from 

 one water type to another, as shown by 

 the data. 



