TEMPERATURE , °C 

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TEMPERATURE ,°C 

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 • 1 



Figure 4.— Monthly profiles of mean temperature (°C), for wanning and cooling periods at seven typical locations (shown by diamond on inset 

 chart); distance from offshore reference point near Honolulu and geographic coordinates as in Figure 3. a. Near Oahu. b. Eastern North 

 Pacific Central Water, c. Subtropical front, d. Transition Zone . e. California front, f. Low-salinity core of the California Current, 

 g. Inshore region of California Current. 



temperature inversions remained in the vertical sections 

 of Appendix 1, e.g., the 15°C isotherm in the 01 April sec- 

 tion, the 15°-17°C isotherms in the mid-April section, 

 the 16°-17°C isotherms in the 01 May section, and the 

 16°C isotherm in the mid-May section. It appears that, 

 on the average, when surface warming begins in the 

 spring and vertical mixing is suppressed, the warmer, 

 higher salinity Eastern North Pacific Central waters 

 spread toward the California coast around 100 m, under- 

 running the low-salinity, modified subarctic waters 

 which are still cool around 50 m. 



In winter months, e.g., mid-January section of Appen- 

 dix 1, there appeared to be a temperature maximum at 

 the base of the mixed layer between 1,200 and 3,000 km 

 along the section. From an examination of individual 

 profiles it was found that these were not typical of usual 

 conditions. There was almost always an isothermal layer 

 to the top of the thermocline. The apparent maximum 

 resulted from the tendency of the three harmonics to give 

 near-surface temperatures for this area in winter which 



were slightly low, 0.1° to 0.2°C. The weak horizontal 

 temperature gradients and vertical exaggeration of the 

 section, amplified the effect in the computer contoured 

 sections. 



Structure Below the Permanent Thermocline 



Below the permanent thermocline, the slopes of the 

 isotherms can be used to separate the section into two 

 regions. The 10°C isotherm is typical. In the western part 

 of the section from Honolulu to about 1,800 km it 

 generally changed depth by less than 50 m, i.e., the slope 

 was less than 3 m/100 km. In the eastern part of the sec- 

 tion, from a point at 2,200 km on the section to near San 

 Francisco (3,800 km) the depth of the 10°C isotherm 

 decreased by 150 to 200 m, or a slope of greater than 9 

 m/100 km. The smaller slopes are associated with the 

 Eastern North Pacific Central waters, while the steeper 

 slopes were associated with both the California Current 

 and Transition Zone regions. 



