from these variables. For example, one branch of the forking tongue of 

 warm water is associated with the high velocity current in the vicinity 

 of station 50, and the other with the current at station 42. The latter 

 current continues past the southern tip of Hawaii and corresponds to the 

 large salinity and density gradient in that region. The clockwise vortex 

 centered in the vicinity of station 49 is again apparent fronn both the sa- 

 linity cuid density distribution, as is also the southeasterly setting current 

 near station 58. In Kauai Channel the tongue of high- salinity water is 

 compatible with the dynamic topography, which shows a strong south- 

 westerly setting current coming from the vicinity of the high- salinity 

 source area northwest of the main survey region. 



North of the island chain the surface variables are of little help 

 in deducing the flow pattern and, as before, it is expected that the sub- 

 surface distribution of variables will help to clarify the picture. 



Subsurface Circulation 



As in the case of cruise 17, investigation of the subsurface 

 circulation involved the two internriediate systems. The depth of the 

 24. 5 sigma-t surface associated with the salinity maximum and the depth 

 of the 26. 5 sigma-t surface associated with the salinity minimum are 

 shown in figures 17 and 18. -They indicate that the vortices revealed by 

 the surface dynamic topography do not always extend through the two in- 

 termediate flow systems. For example, the vortex near station 39, 

 southwest of Oahu, is clearly apparent on figure 17 but not on figure 18, 

 whereas that at station 49 is apparent on both sigma-t surfaces. North 

 of the island chain the vortex at station 23 is apparent on figure 17 only, 

 and that at station 1 is well pronounced on the 26. 5 sigma-t surface only. 

 To illustrate that the complex surface structure extends to great depths, 

 figure 19, showing the depth of the 27.2 sigma-t surface, has been 

 included. 



It is interesting to note in figure 17 the rise of the 24. 5 sigma-t 

 surface northward until at approximately 26 N. it reaches the sea sur- 

 face. On the basis of isentropic theory this would be the latitude where 

 the maximum salinity water originates (Sverdrup et al. 1942:141-146) • 



In figure 20, showing the surface dynamic heights relative to the 

 300-in. level, the four vortices mentioned above are readily distinguish- 

 able. 



In figure 21, the dynamic heights at 300 m. relative to the 1, 000-m. 

 level, the vortex at station 49 appears considerably weaker and that at 

 station 39 is indistinguishable. North of the island chain the vortex at 



15 



