The first noticeable change in the tenn- 

 perature distribution occurs at about 50 na. 

 {fig. 30). At this depth, upwelling is still 

 prominent off western Lower California, as is 

 the southward extension of this water (note 

 16° to 20° C. isotherms). The frontal system, 

 however, has largely disappeared. Weak up- 

 welling off the east coast of the entrance to 

 the Gulf is still evident. The intrusion of the 

 18° and 19° C. isotherms northward to the 

 Gulf suggests the way California Current 

 water may have arrived at station 9, which 

 had a node of relatively low- salinity water 

 between about 30 and 50 m. deep. 



The data (Scripps Institution of Oceanog- 

 raphy, 1967) show that the form of the dis- 

 tribution at 50 m. is not much changed at 100 m. 

 Upwelling off Lower California and the Mexican 

 mainland is no longer detectable, but the 

 strong gradient roughly parallel to the coast 

 of Lower California is still present, though 

 farther offshore. The possible advection from 

 the southwest, mentioned above, seems to be 

 still present. The sanne is true at 150 m.. 



though no other feature noted above persists 

 at that depth. 



Salinity 



Figure 31 depicts the salinity distributions 

 at the 10-m. depth. The most important feature 

 is, again, the frontal system between the Gulf 

 water and upwelled California Current water. 

 This upwelled water is identified by low 

 salinities comparable to those in the sub- 

 surface minimum. It extends far south from 

 the coast to stations 15 and 28, and westward 

 to station 20. Farther west is an apparent 

 intrusion of water of higher salinity (JJ34.60 

 p.p.t.) from the south; this advection accounts 

 for the high salinities at the surface at station 

 143.60 (fig. 16) and can be ascribed to Sub- 

 tropical Surface Water, rather than Central 

 Pacific water which I formerly suggested as 

 a possibility (Griffiths, 1965). The frontal 

 system has two parts: one between Gulf Sur- 

 face Water and California Current Surface 



24" 

 N. 



22< 



20°- 



II4°W. 112° 110° 108° 106° 



Figure 30.— Horizontal temperature distributional 50 m. -depth for part of CalCOFI cruise 6004- Band for cruise TO-60-1. 



35 



