352 



OCEANOGRAPHIC INVESTIGATIONS 



to 55° F) predominating. The variation of the temperature with depth indicated that generally a 

 two-layered water structure was present. The region separating the two water masses, i.e., 

 thermocline, varied both in thickness and depth; however, the maximum depth of the bottom of 

 the thermocline never exceeded 46 m (150 ft). The thermal gradient within 15 m (50 ft) of the 

 bottom was very weak, never exceeding 1°F variation over this depth interval. 



In order to monitor the outside water temperature from within Sealab, a mercury stem 

 thermometer was positioned so it could be easily read from a port within the lab area (Fig. 

 132). Readings were made by the watch crew and were entered in the Sealab log periodically. 

 This thermometer was an immersion mercury stem thermometer in a protective housing. 

 These thermometers, normally used at the surface, may be affected by the pressure at 61 m 

 (200 ft), and a calibration check will be made to determine the depth- correction factor. 



Fig. 132. Aquanaut Dowling checks the outside water temperature from 

 a stem thermometer hanging outside the Sealab II viewing port 



Currents— Current speed and direction in the vicinity of Sealab were monitored by two 

 sell- contained recording type Geodyne current meters, Model A- 100. These were located ap- 

 proximately 27 m (90 ft) away from Sealab (Fig. 130). The data from these instruments were 

 recorded digitally on film at a 15-min sampling interval and are presently being processed 

 for future analysis. 



During Team 2's occupancy of Sealab, estimates of current speed were made by the writ- 

 ers while diving by timing the drift of particulate matter over known distances. Maximum 

 current- speed observed by this technique was approximately 5 cm/sec (0.1 knot). 



Water Clarity — Measurements of water clarity were made with an S.I.O. water clarity 

 meter (4) which was lowered from the surface to within approximately 3 m (10 ft) from the 

 bottom (Fig. 130). This instrument recorded both the beam- attenuation coefficient and the 



