processed data, consisting largely of profiles 

 and distribution of the various fields at the sea 

 surface and on surfaces of constant thermo- 

 steric anomaly, are included in this report (figs. 

 105 through 144). 



LABORATORY METHODS AND TECHNIQUES 



Most of the methods used in the chemical 

 analyses and in preparing the graphs of the dis- 

 tribution of the various fields have been des- 

 cribed in previous reports (Cromwell 1951, 

 Stroup 1954, McGary and Stroup 1956, McGary, 

 Jones, and Austin 1956, King et al. 1957). Only 

 the procedures that varied to some degree from 

 those of previous reports will be discussed. 



The salinity determinations were made by 

 anew modification of Fajan's adsorption indica- 

 tor method developed by~Van Landingham (1957) 

 and adapted to Knudsen's techniques for sea 

 water. It gives a much sharper end point than 

 the potassium chromate indicator and permits a 

 routine precision of about 0. 03 percent. 



The relative density profiles and surfaces 

 for Charles H. Gilbert cruise 17 (figs. 21-24) 

 and Hugh M. Smith cruise 27 (figs. 74-77) are 

 expressed in the terms of sigma-t (LaFond 

 1951). Following the suggestion of Montgomery 

 and Wooster (1954), the use of sigma-t was re- 

 placed with the thermosteric anomaly ( 6 ) in 

 the plots of Hugh M. Sm ith cruise 30 (figs. 120- 

 122). The latter consists of the salinity and 

 temperature terms of the anomaly of specific 

 volume, i. e. 



t 



st 



Montgomery and Wooster defined thermosteric 

 anomaly as "the anomaly of specific volume 

 (steric anomaly) that would be attained if the 

 water were changed isothermally to a standard 

 pressure of one atmosphere" and assigned the 

 dimensions centiliters per ton (cl. /ton). The 

 advantage of the thermosteric anomaly is that, 

 if extreme precision is not desired, it c a n be 

 used for graphical hydrostatic computations for 

 the upper 500- 1 ,000 m. Montgomery and Wooster 

 found that, in the equatorial Pacific, the range 

 of the pressure terms amounted to only 6 cl. /ton, 

 which is 3 cm. in thickness for a 500-db. layer. 



Two different methods were also employed 

 in making the hydrostatic calculations. Those 

 for Charles H. Gilbert cruise 17 (figs. 2-4 and 

 8-12) and for Hugh M. Smith 27 (figs. 48-52and 

 58-62) were calculated from the equations de- 

 veloped by Ekman in the manner described by 



LaFond ( 1 95 1), whereas those for Hugh M. Smith 

 cruise 30 (figs. 106-109 and 114-118) were 

 computed by a graphical method developed by 

 Klein (MS.). 2^ 



The zonal (east-west) components of the 

 geostrophic currents were computed and con- 

 toured for all three cruises (figs. 5-7, 53-57, 

 and 110-113). This was done to permit future 

 calculations of the volume transport through the 

 upper 1,000 m. of each section. The currents 

 were computed by the formulae derived by 

 Sandstrom and Helland-Hansen (LaFond 1951, 

 p. 17, and Cromwell 1951). Briefly, the pro- 

 cedure was to compute the mean current for 

 each degree of latitude at each depth by using 

 the dynamic heights from the isobaric surface 

 profiles. The values were then plotted at the 

 mid-point of each degree of latitude and at the 

 proper depth. The velocity field was then con- 

 toured assuming that the computed values 

 represented the velocity at each point. 



LITERATURE CITED 



CALLAWAY, R. J. 



1957. Cceanographic and meteorological 

 observations in the* northeast and 

 central North Pacific, July - 

 December 1956. U. S. Fish and 

 Wildlife Service, Spec. Sci. Rept. -- 

 Fish. No. 230, 49 p. 



CROMWELL, T. 



1951. Mid-Pacific oceanography, January - 

 March 1950. U. S. Fish and Wild- 

 life Service, Spec. Sci. Rept. --Fish. 

 No. 54, 76 p. 



KING, J. E. , T. S. AUSTIN, and M. S. DOTY 

 1957. Preliminary report on Expedition 

 EASTROPIC. U. S. Fish and Wild- 

 life Service, Spec. Sci. Rept. --Fish. 

 No. 201, 155 p. 



LaFOND, E. C. 



1951. Processing oceanographic data. U. S. 

 Navy Hydrographic Office Pub. No. 

 614, 114 p. 



±1 "A new method for processing oceano- 

 graphic data, " unpublished manuscript by Hans 

 Klein, Scripps Institution of Oceanography. 



