time of the year one would expect sur- 

 face temperatures between 12° and 

 i4°C. and temperatures at 170 meters 

 of 7°-8°C or less. Data from the 

 animal, however, indicated tempera- 

 tures-at-depths of 100-170 meters 

 ranging from 10° to 14°C. If these 

 levels were indeed accurate, a signifi- 

 cant temperature inversion layer was 

 present. This cruise was terminated at 

 2100 hours on 21 March 1972. after 

 having recorded data for approximate- 

 ly 24 hours. In addition to the temper- 

 ature-at-depth data, the following 

 observations were made: 



1. The animal was offshore 1-2 

 nautical miles after sunset, moved 

 inshore 100-200 meters from the 

 beach post -sunrise. 



2. The diving pattern at night was 

 regular, as compared to an erratic 

 pattern during daylight hours. 



3. The animal was observed in 

 Dana Cove along with three other 

 gray whales of a similar size range. 

 All four animals left the Cove in late 

 afternoon. 



4. The mean time between trans- 

 missions was significantly longer from 

 1600 to 0400 hours than during the 

 remainder of the day (Figure 8). 



Since transmissions were more pre- 

 dictable after sunset, our aircraft data 

 acquisition flights were scheduled at 

 night. Under this plan, data were col- 

 lected on 28 and 29 March from the 

 S-2 tracker aircraft in the vicinity of 

 Dana Point, Calif. The recorded data 

 from these flights indicated dives of 

 50-80 meters and temperatures of 

 I2°-14°C. The observations that the 

 animal moved offshore (1-4 miles) at 

 night were verified. 



No readily apparent explanation 

 was available for the relatively high 

 temperatures recorded at depth on 

 20-21 March. To check on these 

 measurements, the RV Sen Sec was 

 sent to the Dana Point area to work 

 from 6 April 1972 through 10 April 

 1972. equipped with an expendable 

 bathythermograph (XBT) system ca- 

 pable of measuring temperature versus 

 depth over a range of 0°C-30°C to 

 depths of 450 meters. During the 



Figure 9. — A composite of three expendable 

 bathytliermograph plots collected 2 miles oil 

 Dana Point, Calilornia, at 1700 hours on 10 

 April 1972. 



period 6-7 April, the area south of 

 Dana Point was searched and no con- 

 tact was made with the animal, al- 

 though one small 7-8 meter whale was 

 sighted. The XBT data, however, in- 

 dicated surface temperatures of approx- 

 imately 13°C which dropped to 6°C 

 at 300 meters, with no obvious Iher- 

 mocline or temperature inversion. 

 Late on 7 April, a search was made 

 north of the Dana Point area by auto- 

 mobile and signal acquisition was 

 made from the Huntington Beach pier 

 at 1600 hours. Observers on the pier 

 claimed to have sighted a small Cali- 

 fornia gray whale with a radio pack 

 swimming north 100 meters off the 

 end of the oi'^'- at 1000 hours on that 

 same day. Our signal acquisition was 

 on a bearing of 280°T which would 



Figure 10. — A composite of three expendable 

 bathythermograph plots collected 1.7 miles off 

 Laguna Beach, California, at 1800 hours on 10 

 April 1972, compared to temperature versus depth 

 data collected from Gigi on 20 March 1972. 



place the animal between Seal Beach 

 and Santa Catalina Island. 



On 10 April 1972. the RV Sea See 

 started a search north of Dana Point 

 at 1600 hours. The first XBT station 

 was at 1700 hours. 2 miles off Dana 

 Point. A plot of temperature versus 

 depth representative of the three mea- 

 surements taken at this location is 

 presented in Figure 9. The vessel 

 moved north to approximately the 

 same location where the temperature- 

 at-depth data were collected from the 

 whale on 20 March. Of major interest 

 here is indication from the XBT data 

 that a rather significant temperature 

 inversion did exist in this area. A plot 

 of the XBT station taken at 1800 

 hours on 10 April. 2 miles off Laguna 

 Beach compared to the temperature- 

 at-depth data transmitted from the 

 whale is illustrated in Figure 10. It 

 should be noted that although the re- 

 lationship between the XBT and whale 

 data appears to be comparable at 

 depths of 100-200 meters, these are 

 preliminary data. Conclusion should 

 not be made without further verifica- 

 tion of the thermal inversion shown 

 in Figure 10. It is possible that the 

 outfall of the San Onofre nuclear 

 power plant north of this location is 

 dumping warm water back into the 

 sea. It has also been shown that at 

 this time of year the mean geostrophic 

 flow at 200 meters has northbound 

 components (Wyllie, 1966). Depend- 

 ing on the temperature, volume, and 

 depth of the San Onofre effluent it is 

 not inconceivable that inversions such 

 as that shown in Figure 9 could result. 

 This, however, is pure speculation at 

 this point. 



ACKNOWLEDGMENTS 



This study was accomplished under 

 funding from NASA. Defense Pur- 

 chase request A-70496A, RTOP 160- 

 75-81, Task 01, Ames Research Cen- 

 ter, Moffett Field, California. Addi- 

 tional funding support was received 

 from the Naval Undersea Center, San 

 Diego, California, Independent Re- 

 search project ROOO-OI. All of the 

 electronic equipment used to instru- 



57 



