at the surface relative to 500 m. , where the northwesterly current 

 impinging on the island chain is deflected to the northwest and southeast. 



Bathythermograph Data 



As before, the bathythermograph data have been included as a 

 record only and are presented by vertical sections in figure 35. 



Inorganic Phosphate 



On Hugh M. Smith cruise 21 good, reproducible inorganic 

 phosphate data, analyzed aboard ship by the method described by Wooster 

 and Rakestraw (1951), were obtained. The surface values were plotted 

 on figure 36 and show little variation. The average phosphate-phosphorus 

 concentration on the windward side of the island chain was approximately 

 0.2 (ig-at/1 and on the leeward side 0.3 [Jig-at/l. A tongue of low-phosphate 

 water (less than 0.2 [j.g-at/1) reached into the survey region between sta- 

 tions 5 and 9 and extended toward the island of Hawaii. This is in good 

 agreement with the surface currents as shown in figure 29. A tongue with 

 a high phosphate concentration (greater than 0.4 |jig-at/l) appears between 

 stations 58 and 60 and extends to station 39, between the counterclockwise 

 and clockwise vortices centered in the vicinity of stations 51 and 49 (fig. 29). 



Figure 37 dhows the phosphate distribution on the 24. 5 sigma-t 

 surface. In general the average concentration is lower on the windward 

 side (0.2 fig-at/l) than on the leeward side (0.3 fig-at/l). Interesting to 

 note is the similarity of the isopleth structure of phosphate-phosphorus 

 cind salinity (fig. 31) on the windward side of the island chain. On the 

 leeward side, the outstanding feature is the pocket of low-phosphate water 

 (less than 0.2 fj.g-at/1) in a region where the average concentration is 

 greater than 0. 3 (ig-at/l. This pocket is located in the vicinity of sta- 

 tion 39, to the northeast of the clockwise vortex (fig. 29), within a tongue 

 of lower phosphate water extending southward through Kaiwi Channel. 



The phosphate distribution on the 26. 5 sigma-t surface is shown 

 in figure 38, where again the concentration is lower on the windward side 

 (generally less than 2 fig-at/l) than on the leeward side (generally greater 

 than 2 (ig-at/1). A tongue of lower phosphate water reaches southward 

 through Kauai Channel toward station 49, and ajiother through Alenuihaha 

 Channel to station 38. Again there are similarities in the isopleth struc- 

 ture of the phosphate and salinity concentration (fig. 33) on the 26. 5 

 sigma-t surface. 



24 



