UNDERWATER WEATHER STATION 383 



Set five plastic bottom drift indicators outside. In 20 minutes they had drifted downslope 

 10 ft. Net drift of sediment is also downslope. A steady current, enough to clean off large ob- 

 jects on the bottom, is evident. A 35-pound Danforth anchor on the sand slope has been ex- 

 posed for two days. Water temperature is 13.5°C, well mixed down to 230-ft depth. 



1600— Very steady up and onshore current. Plankton moves 24 in. in 12-15 sec; 1730— 

 current changed to offshore, 24 in. in 13 sec; 1800— current is onshore, changed direction 

 very quickly. 



Visibility reduced considerably today following wind waves. Heavy red tide this p.m. 

 Sundown at 1900. Visibility 2 ft with hand-held light. 



7th Day 



Mixed current— short on and offshore surge. Plankton moves 24 in. in 20 sec. Heavy red 

 tide last evening, came down fast from seaward. Heavy watch day. Very slight onshore cur- 

 rent all day. Red tide sinking to sea floor. 



8th Day 



Little current detected from ports. Fine plankton in early morning drifting down and 

 slightly offshore— visibility bad. By mid-morning, water became very clear, the clearest wa- 

 ter we have observed, 30 ft visibility with natural light. Worked locating underwater weather 

 station. Anchored weather station platform. 



1800— visibility bad again, more red tide. Visibility changed quickly. Plankton moves 24 

 in. in 21 sec with offshore net drift. Continuous offshore flow with slight fluctuation in veloc- 

 ity. 1800-dark. 



9th Day 



Dense red tide. Fish fill the ports, making current observations difficult. Slight offshore 

 and down net drift. Clouds of sediment rise 5 ft above the bottom from divers working on the 

 weather station. Drift is slow to clear sediment from the area. Set underwater weather plat- 

 form today. 



10th Day 



Temperature 13.5°C, warm. Visibility bad. Slight offshore current, plankton sink slowly. 

 Trajectory is 8 sec down, 8 sec off, 8 sec down, etc. Net offshore, 8-9 in. in 16 sec. Steady 

 temperature increase for three days, 46-48-50-55°F. 



1100— short periods of up and offshore current. Net transport offshore and down, 2 ft in 15 

 sec. Mid-afternoon to dark— trajectory of plankton shows the following periodicity in cycle: (a) 

 horizontal offshore movement for 8 sec, followed by (b) up movement for 8 sec, etc. The net 

 drift is offshore and up. 



nth Day 



Upper direction vane (1) and Savonius rotor (2) on weather station in operation. Rustrak 

 recorders in Sealab are recording. Recorded current of 0.8 knot. During diver inspection, 

 sensor 2 turning one revolution in 2 sec and direction vane indicated current flow offshore. 

 Sensor 5 turning one revolution in 4 sec. Analog record of sensor 2 indicates 0.1 knot steady 

 during day, increased at 1700 to full scale (almost 2 knots) on the upper current sensor (2) and 

 to 1 knot on the lower current sensor (5). Current direction offshore. 



