features were pointed out, but in general no attennpt has been made to 

 interpret or explain them. It is felt that the information gained fronn 

 each cruise is but a fragn^ent of the oceanographic picture of the 

 Hawaiian Islands region and a more complete understanding must wait 

 until all the available data can be synthesized. 



Surface Variables 



The surface layer has been given special attention because in it 

 the primary production of the sea takes place. The surface parameters 

 of temperature, salinity, and density can also be used as indices of 

 seasonal and longer period changes in the oceanic environment. 



An understanding of the surface temperature is particularly 

 useful because of the easy manner in which it can be measured by ther- 

 mometer and bath -thermograph. Generally temperature is the important 

 independent variable in the density distribution, which in turn is used to 

 obtain the relative current picture. In the Hawaiian Islands region, how- 

 ever, it was shown that salinity is also important in the distribution of 

 surface density. 



Table 5 below summarizes for each cruise the averaged surface 

 tennperature, salinity, and density (sigma-t) in the four sections of the 

 survey region. On the basis of data from one winter and two summer 

 cruises, one can only hint at the seasonal trends and point to interesting 

 features. By studying the temperature, for example, one finds that the 

 seasonal range is about 4 F. , which is less than the extreme range of 

 almost 6 F. encountered during cruise 17. The extreme ranges on the 

 windward and leeward sides of the island chain on cruises 20 and 21 did 

 not indicate any clear seasonal trend. The leeward side of the island 

 chain was dominated during cruise 1 7 by a large counterclockwise vortex, 

 whereas during cruises 20 and 21 there were a number of smaller vor- 

 tices in this region. Thus, the temperature range might indicate the 

 type of vortex activity. 



Although the average salinities changed from cruise to cruise, 

 no seasonal trend is indicated. Figures of the surface salinity distri- 

 bution suggest that the changes are not due to island runoff only, but 

 also to varying concentrations outside the survey region. 



It is interesting to note that the salinity range in each cruise 

 shows a seasonal trend. On cruise 17 (summer) the extreme range 

 was about 0.3 /oo, on cruise 20 (winter) 0.9 /oo, and on cruise 21 

 (summer) 0. 5 /oo. Another interesting feature is the slightly 



26 



