100 



Water 



Figure 86. Comparison of tem- 

 perature, phosphate, dynamic 

 topography, and diatom con- 

 centration at the surface for 

 the E. W. Scripps cruise of June 

 7-16,1938. Note the similarity 

 of all four maps and their rela- 

 tionship to the closely cross- 

 hatched Santa Rosa-Cortes 

 Ridge. Transparency of water 

 in terms of Secchi disk read- 

 ings in meters is based on 

 about 1200 measurements, 

 mostly in waters atop the main- 

 land shelf; the depth is that at 

 which a 30-cm white disk dis- 

 appears from view. The color 

 of water is the per cent of yel- 

 low solution in a mixture of 

 basic yellow and basic blue; 

 yellow was made by dissolving 

 1 gram KXrOj in 200 ml wa- 

 ter, blue by dissolving 2 grams 

 CuSO, and 4 grams (NH3)._,C03 

 in 200 ml water. Method and 

 much of color data by D. W. 

 Scholl. 



sea level of as much as 20 cm within the 

 area of Chart I (Fig. 87). During most of 

 the cruises there existed a trough extending 

 south of Point Conception to the vicinity of 

 San Nicolas Island. Sea level was usually 

 highest west of the trough near the south- 

 west corner of Chart I, the point farthest 

 from shore. A secondary high commonly 

 was present in a ridge east of the trough, 

 trending southeasterly from near Santa Cat- 

 alina Island about 30 miles offshore. Nearer 

 shore a secondary low was shown by data 

 of most cruises having stations in that area. 

 Water tends to flow downhill from the 

 areas of high sea level, but owing to the de- 

 flection caused by earth rotation (Corioli's 

 force), it is deflected to the right of this path 

 in the Northern Hemisphere. In a friction- 

 less medium the deflection is theoretically at 



a 90° angle to the slope; thus, the current is 

 assumed to move along the contours of 

 dynamic topography in the direction such 

 that high topography is on the right-hand 

 side of an observer facing the same direc- 

 tion that the current is moving. Arrows 

 drawn on the contours of dynamic topog- 

 raphy show the direction of current flow, 

 and the spacing of the contours is inversely 

 proportional to the velocity of the current. 

 In the five cruises between 1950 and 1952 

 chosen as examples the surface current with 

 respect to the 300-decibar level flows at 

 velocities as great as 30 cm/sec, or 0.6 knot. 

 Usually, the greatest velocities occur in the 

 area farthest from shore, where the eastern 

 side of the southeasterly flowing California 

 Current is encountered. Like the Gulf 

 Stream (Ford and Miller, 1952; von Arx, 



