of the eddy (fig. 4, panels B and C). A strong northerly flow is indicated by the 

 depth and sharpness of the thermocline along the southwest coast of Hawaii. 



The effects of diurnal heating were shown by the small pockets of warm 

 water on the surface at stations 6, 10, and 14. In each case the BT lowerings were 

 made during daylight and when the wind was Beaufort force 2 or less. 



In order to estimate the amplitude of internal waves that could be ex- 

 pected in the area, the vessel was permitted to drift from 1930a December 12 to 

 1000& December 13 at approximately 19°41'i»-, 156°15'V«., while bathythermograph 

 lowerings were made at half -hour intervals. As was expected (Sverdrup et al. 1946, 

 p. 588), the results (fig. 5) show that the amplitude was greatest at the top of 

 the thermocline and decreased rapidly with depth. The 75°F. isotherm, which was 

 just below the thermocline, had a maximum change of depth of 115 feet, while the 

 60°F. isotherm had a change of only 80 feet. Although the data indicate the pre- 

 sence of waves of several periods, the time covered by the observations was too 

 brief to permit further analysis of the data. 



Sigma-t 



The distribution of sigma-t, as shown by the cross sections (fig. 6) and 

 lateral surfaces (fig. 7) is consistent with the dynamic topography. The cyclonic 

 nature of the eddy is shown by the doming of the isopleths in the vicinity of 

 station 6. 



The topography of the 23.6, 24. 0, 25. 0, and 26.0 surfaces indicates that 

 the source of most of the water in the eddy was from flow around the southern coast 

 of Hawaii . Flow through Alenuihaha Channel is not indicated until the depth of the 

 25.0 and 26.0 surfaces is reached and then it is relatively weak. 



The 23.6 surface was selected for contouring because it was the greatest 

 value that intersected the surface and therefore should illustrate the greatest 

 depth from which nutrients could be brought to the surface by isentropic flow. 

 However, since the difference in density is greater than the difference In temper- 

 ature on the two sides of the eddy would indicate, it is probably Indicative of the 

 degree of intrusion of less saline water that was being driven into the area around 

 the southern tip of Hawaii by the southeasterly winds which predominated during the 

 cruise period. 



Salinity 



The salinity cross sections (fig. 8), surface salinity (fig. 9), and 

 plots of salinity on the sigma-t surfaces (fig. 7) show the degree of the intrusion 

 of water from the southeast. The surface salinities show that water having a sa- 

 linity of less than 35.0 °/oo had entered between stations 1 and 2 and had pene- 

 trated three-quarters of the way around the eddy. Below the surface its progress 

 is shown by the trough of low salinity on the 24. sigma-t surface and by the 

 tongue of low salinity water that had penetrated to station 9 on the 25.0 surface. 



Dissolved Oxygen 



The vertical distribution of dissolved oxygen (fig. 10) is very similar 

 to that shown for 20°N. latitude in the Carnegie section (Sverdrup et al. 194t>, 

 p. 710) except for the O2 maximum of greater than 5.0 ml/1. The Carnegie data show 

 that this corresponds to the S °/oo maximum, and hence it can be attributed to con- 

 tact with the atmosphere in the region northeast of the islands, where evaporation 

 and cooling caused the surface waters to sink and spread out as an intermediate 

 layer. In figure 10 it is present only as a small elongated cell at about 100 m, 

 on an axis through stations 2 eind 15 and corresponds to the trough of low salinity 

 which appeared on the 23.6 and 24. slgma-t surfaces. 



10 



