A prolonged maritime strike in 1971 interrupted the 

 series for two periods of nearly 3 and 5 mo each. A faster 

 (22 kn) ship, Hawaiian Enterprise, made most of the sec- 

 tions in 1971 and 1972, resulting in more frequent sec- 

 tions but with greater spacing between observations. As a 

 part of the International Decade of Ocean Exploration 

 (TDOE) programs, we began instrumenting other ships in 

 late 1972 for other routes, but which also would make 

 sections irregularly on the San Francisco route. Using 

 these ships, the frequency of sections on the San Fran- 

 cisco route was increased in 1973 and intense coverage 

 was obtained in 1974. 



For the entire period from June 1966 through 

 December 1974 there was a total of 4,913 observations 

 (Table 1). A number of the sections did not have com- 

 plete coverage, with the coverage generally being poorest 

 near either end of the route. This should be considered 

 when interpreting the computer analyses which will be 

 presented. 



Instrumentation 



The basic sensing and recording system used through- 

 out the period was the Sippican XBT system. Progres- 

 sive improvements were made in the recorder by the 

 manufacturer — some partially due to the field ex- 

 periences from this project — during the first few years, 

 1966-68. Since then, the recorder, with pressure sensitive 

 paper and an option switch for 460 m (1,500 ft) or 760 m 



(2,500 ft) depth recording, has remained essentially un- 

 changed. 



The XBT system initially installed aboard the Cali- 

 fornian included an experimental digitizer (developed by 

 FNWC) with analog signal input from a retransmitting 

 slidewire in the XBT recorder and digital output onto a 

 5-level punched paper tape at depth intervals of slightly 

 less than 3 m (Saur and Stewart 1967). This was a dual 

 purpose output for testing radio transmission of data to 

 FNWC and for subsequent computer conversion, ashore, 

 onto magnetic tape for permanent archives. The digitizer 

 system became unstable after April 1969 which made the 

 output unsuitable for archiving data. Although commer- 

 cial digitizing systems were tried with some of the new 

 recorders installed on other ships in 1971 and 1972, all of 

 the data used herein from May 1969 onward were derived 

 from the analog traces. 



Sippican model T-4 XBT probes (460 m) were used 

 during the first 1.5 yr of the project. We switched to use 

 of model T-7 probes (760 m) in November 1967, to try to 

 minimize probe-to-probe temperature errors by cor- 

 recting deep temperatures to a smoothed deep level 

 temperature (e.g., 600 or 700 m). This plan proved to be 

 unworkable because the deep level temperatures could 

 be offset to warmer temperatures by insulation failures 

 on the wire and such a bias could not always be 

 recognized with certainty by examination of the analog 

 traces or vertical sections. At a later date mesoscale ed- 

 dies were discovered and appeared to have deep 



Table 1 



—Number of expendable bathythermograph (XBT) sections by cooperating ship 

 and total observations by year on the San Francisco-Honolulu route. 













Year 











Total 





1966 



1967 



1968 



1969 



1970 



1971 



1972 



1973 



1974 



sections 



Matson Navigation Co. 

 Californian 

 Hawaiian Enterprise 

 Hawaiian Citizen 

 Hawaiian Queen 



10 



15 



18 



15 



15 



5 

 4 



'18 



19 



6 



2 26 



1 



10 



84 



67 



1 



10 



Chevron Shipping Co. 

 Idaho Standard 

 Washington Standard 

 McGarragill 

 Chevron Californian 

 Chevron Mississippi 











3 

 2 



1 





1 

 1 



2 

 4 



1 



3 

 2 

 1 

 4 

 5 



States Lines 

 Michigan 

 Idaho 













1 



1 









1 

 1 



American President Line 

 President Cleveland 













1 









1 



Pacific Far East Line 

 Monterey 

 Mariposa 

















2 



1 

 9 



3 

 9 



U.S. Coast Guard 

 USCGC Midgett 

















2 





2 



Total sections 

 Total observations 



10 

 204 



15 

 329 



18 

 550 



15 

 435 



21 

 592 



12 

 229 



20 

 453 



29 

 635 



54 

 1,486 



194 

 4,913 



'11-16 February 1968 section had two XBT drops at each 4-h interval. 



2 Includes one special section, 27 April-1 May 1974, with hourly observations by R. L. Bernstein 

 and C. A. Collins. 



