24 



show the sharp temperature change associated with the thermo- 

 cline in the tropics--£rom about 25° C. at 50 to 100 meters to 

 10°C. at 200 to 300 meters, as well as the tongues of low and 

 high salinity associated with the thermooline and the region 

 of low oxygen concentration below the thermocline. All of 

 these features are characteristic of the tropical ocean, and 

 all are probably of considerable importance to animals living 

 in these regions. 



In addition to analyzing data collected by other agencies, 

 the Laboratory's oceanographers have also been active in 

 collecting data; in the central Pacific Ocean, approximately 

 80 percent of the oceanographic data was collected by the 

 Laboratory's research vessels. The most recent studies have 

 included the use of three means for direct measurements of 

 currents: drift cards, drogues, and a scale model. 



Drift bottles and cards have been used to study surface 

 currents in the central Pacific since 1961. The drift bottle 

 used by the Biological Laboratory is shown in figure 29, which 

 is a photograph of a poster placed in schools and other public 



buildings in Hawaii in 1961 to publicize the program. These 

 bottles performed well, but took up too much space aboard 

 our research ship and could not be dropped from aircraft, so 

 a drift card was developed that performed as well as the 

 bottles and was considerably more compact and less fragile. 

 Figure 30 shows one of these drift cards, together with the 

 plastic envelope and the weight that was added as ballast. 

 These cards were dropped from aircraft regularly each month 

 to provide information on month-to-month changes in the sur- 

 face currents near the islands. 



N9 065963 



C l-ME «!:*»« 



TO; 



UNITED STATES 

 DEPARTMENT OF THE INTERIOR 



Bureau of commercial fisherifs 



honouolu biological LABORA't*- 



f ao* MTo. HowauLu h.h***' 



us « 



HAVE YOU SEEN ANY OF THESE BOTTLES 7 



EACH BOTTLE CONTAINS 

 SOME SAND BALLAST AND 

 A CARD LIKE THIS=^ 



CUtr TWO 01 JHllt UOMTHS. THl HOHOWIU 



IIOLOeiCAL lASOtATOn IS lllCASIHC AP?MimAUL1 "^1.000 Of THCSC DdFT SOTTllS IHTO 



rm OCCAU MCAt jhc Hawaiian isiamds to stuoi thi cvshhts in the mid-paciuc. pliasc 



KOKIIA. IF yOV FMV AMY OF THF DUFT BOTTICS MAIL THC IMCLOSIO P0STA([-FtCl CAfD. 

 niASl SIMP AU TMC CAtDS tOU FIMt). 



Figure 29. — Poster used to publicize drift bottle 

 program In 1961-62. 



N9 065963 



Figure 30. — Drift card sealed Into plastic envelope. 



Drift bottle returns can provide valuable information on 

 ocean movements both large in scale (fig. 31) and small 

 (fig. 32). 



For example, of the releases shown in figure 31, those 

 made nearest the Equator traveled fastest, at speeds of more 

 than 36 miles a day. Releases away from the Equator moved 

 more slowly; at 10° N. the speeds were about 20 miles a day. 

 while at about 20° N. the speeds dropped to about 12 miles a 

 day. 



Figure 32 shows drift bottle and card releases and returns 

 in the Hawaii area for January through March in 1961, 1962, 

 and 1963. Similar charts showing the year-around pattern of 



