shows the distribution of surface isotherms 

 from the data of the two cruises. Figure 3 

 shows the temperature profile, and figure 4 

 the salinity profile, from stations 7 to 22 of 

 cruise TO-60-1. Because no hydrocast was 

 made at station 15, the cool surface water was 

 not detected by that method; it was detected by 

 BT, however, and is shown in figure 3 by 

 dashed contours (19° and 20° C. isotherms). 

 The extensive oxygen minimum, typical of the 

 eastern tropical Pacific Ocean, is superim- 

 posed on these profiles. 



There are at least three kinds of surface 

 water (upper 150 m.) off southern Lower 

 California (Roden and Groves, 1959): (1) Cali- 

 fornia Current water, from the north, flowing 

 usually southeastwards off the western coast, 

 cool and of low salinity (S<34.60%o); (2) equa- 

 torial Pacific water, from the southeast, flow- 



STA. NQ 22 20 



21 20 20 



ing usually northwestwards, warmest and of 

 intermediate salinity (S ~ 34.65 - 34.85/oo) in the 

 area of the Gulf entrance; (3) Gulf of California 

 water, usually flowing out of the Gulf of 

 California on its western side, somewhat cooler 

 and more saline (S ii 34.90%.,) than equatorial 

 Pacific water. It is also possible that warm, 

 relatively high salinity water from the central 

 North Pacific intrudes into the area at the sur- 

 face (Reid, Roden, and Wyllie, 1958; also p. 24, 

 this paper). The Gulf of California is supplied 

 mostly by eastern tropical Pacific water (Roden 

 and Groves, 1959) and probably sometimes by 

 California Current water (note the cell of low 

 salinity at station 9, fig. 4). In the Gulf the 

 temperature of the surface water is raised by 

 insolation and its salinity is raised by evapora- 

 tion (Roden and Groves, 1959). 



200 — 



CO 



UJ 30Q- 



X 

 UJ 



a 



400- 



600- 



- 100 



•200 



400 



500 



.600 



Figure 3. — Temperature profile to 600 m. based on data from hydrocast stations 7-22, TO-60-1; the dashed isotherms 

 (19'-', 20° C.) are from BT data and represent a feature not detected by the sampling pattern of hydrocast stations (figs. 

 1 and 2). Contour interval: 1° C. Note the boundaries (0.1 ml. l."l) of the oxygen minimum layer. 



