20 



RECORDS OF OBSERVATIONS, SCRIPPS INSTITUTION OE OCEANOGRAPHY 



from Point Conception and corresponding to the 

 trough line. Maximum temperatures and ninimum 

 salinities were always located in the offshore 

 area and a secondary temperature maximum occurred 

 off San Diego. 



Temperature and salinity distribution at 200 

 meters . - The temperature and salinity distribu- 

 tion at 200 meters for each of the six cruises is 

 shown in charts 25 to 30. The extreme values and 

 the ranges in conditions are given in table 2. 

 The pattern of distribution in each instance is 

 rather complicated but the range in temperature 

 and salinity is much less than at the higher 

 levels. The most marked difference at this level 

 is that the minimum temperatures are now asso- 

 ciated with minimum salinities, usually in the 

 offshore area, whereas maximum temperatures and 

 salinities always occur in the Counter Current 

 system. Sometimes this generalization does not 

 hold, because of the transport of water of one 

 character into that of another type. Since the 

 seasonal climatic cycle cannot be directly ef- 

 fective at this depth, the fluctuating condi- 

 tions must be ascribed to the shifting currents. 



Dissolved oxygen content at 200 meters. - The 

 distribution of dissolved oxygen at a depth of 

 200 meters for each cruise is shown in charts 

 31 to 36. The extreme values and the range en- 

 countered on each cruise are given in table 2. 

 The minimum values were always found in the 

 Counter Current or in the trough. Occasionally 

 isolated minima, associated v;ith eddies, occurred 

 in the offshore water. The low oxygen content 

 inshore is a characteristic of the water of the 

 Coastal Deep Current, as shown by Sverdrup and 

 Fleming.^ The maximum values for dissolved- 

 oxygen content always occurred in the offshore 

 water and generally in the southwestern part of 

 the area examined. 



Phosphate content at 50 meters . - The dis- 

 solved-inorganic-phosphate content found on 

 Cruises 1, II, and III, at a depth of 50 meters 

 is shown in charts 37 to 39. The values are 

 given as microgram-atoms per kilogram. The pat- 

 tern of distribution in general follov;s that of 

 the temperature, indicating that upwelling is 

 thq chief process bringing phosphate to the sur- 

 face layers. Maximum values were always found 

 north of Point Conception and in the trough line 

 extending south and east. Minimum values always 

 occurred in the offshore water and generally in 

 the southwestern part of the area examined. The 

 highest value was found off Point Conception on 

 Cruise III, showing that the upwelling provided 

 a plentiful supply of nutrients during the vege- 

 tative season. 



Currents and the distribution of properties . - 

 Since the dynamic topography depends upon the 

 distribution of density, one must expect a paral- 

 lelism between the streamlines and the horizontal 

 distribution of 



^Ibid. 



distribution of the isotherms and isohalines, es- 

 pecially of the former. That such an agreement 

 exists may be seen when the surface topography 

 for any cruise is compared with the correspond- 

 ing temperature distribution at 50 meters. Changes 

 in the pattern of flow between cruises are simi- 

 lar to the changes in the distribution of tempera- 

 ture and salinity. Since fluctuations occurred 

 at depths below the zone of direct influence of 

 the local external climatic factors, it seems 

 reasonable to attribute the major part of the 

 changes in conditions to variations in the pat- 

 tern of flow rather than vice versa. Parts of 

 the changes in the currents may be due to local 

 factors such as the winds, but others are prob- 

 ably brought about by agencies operating beyond 

 the area covered by our investigations. 



The cyclic changes in conditions which might 

 be expected to occur during the course of the 

 year are obscured and complicated by a number of 

 factors. The area covered by these investiga- 

 tions is one of large variations in the lateral 

 distribution of temperature, salinity, oxygen, 

 and probably other components. This is due part- 

 ly to the gradients associated with the flow, but 

 chiefly to the effect of upwelling and to the dif- 

 ferent character of the subsurface water in the 

 offshore area and in the Coastal Deep Current near 

 the coast. Consequently, the changing currents 

 carry with them water of widely differing charac- 

 ter and, in addition to the changes caused by the 

 shifts in the circulation, lateral mixing and the 

 breaking away of eddies lead to a very compli- 

 cated pattern which to a great degree obscures 

 any annual cycle. 



Near the coast upwelling tends to reduce the 

 temperature and to increase the salinity in the 

 surface layers. The upwelling is most active dur- 

 ing the spring and early summer months and tends 

 at that time to lower the temperatures when nor- 

 mally there should be warming of the surface lay- 

 ers. From the data in table 2 it is seen that at 

 and 50 meters minimum temperatures always oc- 

 curred near Point Conception and in or near the 

 trough, and that the annual range of the minima 

 was much less than the range of the maxima. That 

 is to say, in the area off Point Conception and 

 toward the southeast, the upwelling tends to main- 

 tain low and rather uniform temperatures whereas 

 the temperature in the offshore area and in the 

 Counter Current system are rising. 



Part of the complexity of the distribution of 

 properties is due to eddies which transport water 

 of one type into that of another type. These ed- 

 dies are apparently associated with the shifting 

 currents or result from the instability of the 

 current system. These eddies are frequently of 

 such small dimensions that they were only de- 

 tected at single stations. Consequently the com- 

 plexity of the distribution shown in the charts 

 depends to an appreciable degree upon the fact 

 that the observations were obtained at a rela- 

 tively large number of closely spaced stations. 



