increasing trend of salinity from west to east during cruise 17, and a 

 more definite increasing trend from east to west during cruise 20 on 

 both sides of the island chain. During cruise 21 the salinity increased 

 fronn west to east on the windward side and from east to west on the 

 leeward side of the island chain. 



Variations in the average surface sigma-t values show the 

 combined effects of the temperature and salinity variations. The sigma-t 

 values are higher in winter than in summer and for each cruise they are 

 also higher on the windward side of the islands, reflecting the tempera- 

 ture effect. The greater range in extreme values of sigma-t for the win- 

 ter cruise than for the summer cruises reflects the influence of salinity 

 on the density. 



It is interesting to note that the sigma-t values increased from 

 southwest to northeast during the summer cruises and from south to 

 north during the winter cruise. Thus, the relative current due to the 

 surface distribution of mass would drift southeastward in summer and 

 eastward in winter. 



Surface Currents 



The investigation of surface variables was followed by a study of 

 the surface current pattern, which generally was one of complexity with 

 little net transport through the survey region. 



The dynamic topography (fig. 5) of cruise 17 showed that the 

 leeward region was dominated by a large counterclockwise vortex. The 

 currents on the windward side appeared to be very weak, except for one 

 in the region north of Kauai setting southwest at approximately 0.4 knots. 



The dynamic topography of cruise 21 (fig. 29). showed two 

 counterclockwise vortices in the lee of the island chain. The position 

 of the counterclockwise vortex of cruise 17 was now occupied by a large 

 clockwise vortex. The current pattern on the windward side of the 

 island chain also appeared nnore complex than on cruise 17. 



The most confusing current pattern was shown by the dynamic 

 topography of cruise 20 (fig. 15), when both sides of the island chain 

 were dominated by vortex motion apparently without a systematic pattern. 



Subsurface Circulation 



The currents deduced from the surface density (the light water 

 is to the right of an observer facing in the current direction) were not 



28 



