due to insulation defects in the wire link. If 

 the wire breaks in the water, the electrical 

 short causes the pen to move to the high- 

 temperature side of the recorder and remain 

 there. In 71 releases, two failures appearedto 

 result from insulation defects and six from 

 wire breaks. 



NEAR-SURFACE IRREGULARITIES 

 IN THE TRACE 



The rated response time of the thermistor 

 sensor is about 0.1 sec. Thus, it takes 0.3 

 sec. for the thermistor to respond to 95 per- 

 cent of a step change in temperature and 

 during this time the probe descends about 9 

 to 10 ft. (3 m.). When the cycle starts as the 

 probe enters the water, the thermistor is 

 responding to change from its ambient tem- 

 perature in the launcher to water temperature. 

 For most of the observations a small curve 

 appears in the trace between the surface and 

 10 ft. (3 m.), which is a result of the therm- 

 istor response time. No attempt should be 

 made to utilize the record of temperature for 

 depths less than 10 ft. (3 m.) . 



In 12 observations included in this report, 

 the temperature trace exhibited a gradient 

 from the surface to a depth of 20 ft. (6 m.) or 

 greater which was not believed to be valid. 

 This conclusion was reached for several 

 reasons. A large storm had moved through 

 the area preceding the voyage, and the weather 

 remained windy with cooling at the surface, 

 which would create a well-mixed layer. Ex- 

 cellent agreement between the bucket (surface) 

 temperature and the NSRT temperature (8 - 

 9 m. below the surface) verified the isothermal 

 condition in the surface layer. Thus, the near- 

 surface gradient appearing in the trace was 

 judged to be instrumental. In tests made by 

 the manufacturer in probes of the same model 

 (T-3), a few also failed to have the proper 

 response. Since the evidence is not conclusive 

 that the apparently erratic trace was due to 

 the instrument system, the traces are shown 

 as they were recorded, but the doubtful portion 

 (according to our judgment) has beenhachured 

 to draw attention to it. These doubtful gradients 

 occurred at observations 8, 9, 10, 11, 12, 15, 

 17, 28, 29, 31, 52, and 64. We feel that the 

 trace for these observations should be vertical 

 through the hachured portion to connect with 

 the vertical line just below the hachured layer, 

 portraying an isothermal water layer. 



CHARACTERISTICS OF TEMPERATURE 

 SECTIONS 



The temperature section derived from the 

 observations on the outbound leg is shown in 

 figure 7 and that for the inbound leg in figure 8. 

 The isotherms for every 2° F. show the gross 

 features of the temperature structure. The 

 pronounced mixed layer is evident across the 

 entire section, but it becomes progressively 

 shoaler from about long. 140° W. toward the 

 California coast. Similarly the isotherms rise 

 more rapidly in the eastern half of the sec- 

 tions. Both features are evidence of more 

 rapidly moving southward flow, normal to the 

 section, in the eastern part which is occupied 

 by the California Current. 



On the outbound section (fig. 7), the iso- 

 therms show a steep rise at mid-depths at 

 observation 22. This feature is worth noting 

 because a similar rise in the isotherms occurs 

 at observation 39 on the return section (fig. 8). 

 Although the gradients were small at these 

 depths and a slight temperature error could 

 cause such a feature, it seems that this 

 temperature ridge may well be a real feature. 

 Time series sections, such as those planned 

 for this pilot project, should reveal much 

 information on features like this which here- 

 tofore might well have been viewed with sus- 

 picion as instrumental or observational error. 



Because a temperature inversion appeared 

 at observation 55, a special series of closely 

 spaced observations was begun. The tempera- 

 ture structure from the closely spaced XBT 

 observations over a distance of about 45 

 nautical miles (85 km.) reveals a complex 

 structure of maximums and minimums (fig. 9). 



Robert P. Brown of the BCF Tuna Re- 

 sources Laboratory, La Jolla, Calif., has 

 previously noted (unpublished data and per- 

 sonal communication) that similar complicated 

 vertical temperature structure was observed 

 about 500 nautical miles (930 km.) west of 

 Los Angeles. He found this structure was 

 associated with the boundary between the 

 outer edge of the California Current and the 

 Eastern North Pacific Central Water Mass. 

 Roden (1964) has also described the occur- 

 rence of temperature maximums in mechani- 

 cal bathythermograph observations from the 

 Northeast Pacific Ocean. It appears that such 

 structure is characteristic of the outer 

 boundary of the California Current for dis- 

 tances of at least several hundred miles 

 parallel to the California coast. 



