THE PACIFIC OCEAN 



95 



greater thickness, especially in the central part of the 

 section, where at station 48 it reaches to almost 80 me- 

 ters, and at station 45 it exceeds 60 meters, but at sta- 

 tion 51 it reaches to less than 25 meters. The zone of 

 rapid transition sinks as one proceeds to the south along 

 the section. The distribution of temperature does not 

 show any other conspicuous features. 



The salinity has high values at the surface, surpass- 

 ing 36.00 per miUe between stations 47 and 50. A tongue 

 of salinity'above 36.00 per mille stretches past station 

 47 to the north, which indicates a transport of water of 

 high salinity at a depth of about 100 meters. In the south- 

 ern part of the section the intermediate antarctic cur- 

 rent is recognized by the tongue of low salinity at a level 

 of about 700 meters. The axis of the lowest values ap- 

 parently rises as it proceeds toward the north and 

 reaches a level of about 600 meters to the north of sta- 

 tion 48. The axis again nearly coincides with the iso- 

 therm of 6° and this isotherm shows a corresponding 

 but smaller rise. The deep water has the same uniform 

 character as in the preceding section. 



Section X. --Section X (stations 51, 52, and 55 to 60) 

 runs from southeast to northwest from station 51 to 60. 

 The convection layer is thin at all stations, and exceeds 

 30 meters only at stations 55, 56, and 57. The isotherms 

 sink toward the northwest in the upper layers, which in- 

 dicates that we approach the warm-water accumulation. 

 Below 800 meters they run horizontally. 



The salinities are also highest to the northwest, 

 where values above 35.5 per mille are found, and where 

 the course of the isohalines indicates that water of high 

 salinity is spreading toward the southeast. In the most 

 southeastern part of the section we find very low surface 

 salinities, probably characteristic of the easterly cur- 

 rent in this region. The decrease of the surface salinity 

 in a horizontal direction is especially rapid in the region 

 of station 57, and here the northern limit of the easterly 

 current may be sought. The belt of salinity below 34.4 

 per mille at a depth of 600 to 800 meters represents the 

 intermediate antarctic current. The axis of the lowest 

 values is found at approximately 800 meters at station 

 51 and rises to about 650 meters at station 60. At sta- 

 tions 51 to 57 the axis follows the isotherm of 5° but at 

 stations 58 to 60 it follows the isotherm of 5.°5. The 

 isotherms in these 'ayers, however, also show a rise 

 toward the southeast which corresponds to the rise of 

 the axis. The deep water has a temperature which de- 

 creases regularly with increasing depth, but the salinity 

 of the deep water shows a more irregular distribution. 

 At stations 58 to 60 salinities above 34.7 per mille have 

 been observed, being the highest values which were found 

 below the 2000-meter level. 



Section XI. --This section (stations 71 to 93) runs 

 practically east and west, and follows approximately the 

 parallel of 18° from the Peruvian coast to the Samoan 

 Islands. 



In the eastern part of the section, off the South 

 American coast, the convection layer is very thin, only 

 about 20 meters as a rule, but the thickness increases 

 toward the west and exceeds 50 meters at several sta- 

 tions. 



In the western part of the section, which is taken in 

 the central region of the South Pacific Ocean, we find an 

 accumulation of warm water which reaches to a depth of 

 more than 400 meters, if we regard the isotherm of 10° 

 as representing the lower limit of the warm water. High 

 temperatures, above 25°, are found to the west of station 



78 only, and the isotherms of 20° and 15°, which are 

 found at a considerable depth in the central part of the 

 ocean, rise almost to the surface as they approach the 

 coast. The rise of these isotherms indicates an accu- 

 mulation of cold water at the coast, but this accumula- 

 tion is characteristic of the upper layers only because 

 the isotherms below 300 meters are horizontal or sink- 

 ing as they near the coast. Thus all isotherms below the 

 isotherm of 7° are found at a lower level off the Peruvi- 

 an coast than in mid-ocean. 



The salinity distribution in the troposphere is char- 

 acterized by high values to the west of station 77. At 

 most stations a salinity maximum is found at a short 

 distance below the surface and this must be attributed 

 either to the influence of seasonal variations or to the 

 existence of subsurface currents which transport water 

 of high salinities from regions south of the section. The 

 isohalines rise as they approach the South American 

 coast, which shows that the cold water at the coast has a 

 low salinity. The salinity decreases very rapidly with 

 increasing depth between 200 and 300 meters, and at a 

 depth of 600 or 700 meters we find in the whole section 

 low salinities representing the northern part of the in- 

 termediate antarctic current. The axis of the layer of 

 low salinity sinks slightly toward the coast and runs on 

 an average, at a level of about 650 meters in the eastern 

 part. The temperature along the axis is nearly 5.°5 over 

 the whole distance, and the sinking of the axis nearly 

 corresponds to the sinking of the isotherms. The bot- 

 tom water is very uniform, the isotherms running near- 

 ly horizontally, but the salinity appears to be higher at 

 the same level near the South American coast than in 

 mid-ocean. 



Section XII. --Section XII (stations 40 to 45) also 

 runs approximately east and west and follows nearly the 

 parallel of 2° from the South American coast to longi- 

 tude 105°. The section thus represents conditions in the 

 eastern part of the Pacific very near the equator. 



The convection layer is very thin at the coast but 

 increases systematically toward the west, and has a 

 thickness of nearly 60 meters at station 45. The tem- 

 perature in the upper layer is very low, remaining be- 

 low 23° at all stations and being lower than 20° at sta- 

 tions 42 and 43. These stations were within the area of 

 low temperature which, according to the chart showing 

 the temperature distribution at the surface, stretches 

 toward the west from the South American coast. The 

 temperature decreases rapidly directly below the con- 

 vection layer, but this rapid decrease takes place in a 

 short distance only. 



The salinities on the whole are low, especially at a 

 short distance from the coast, and show a maximum at a 

 level of approximately 100 meters, perhaps representing 

 a transport of water from the southwest at this level. A 

 layer of low salinity is also found in this section, and it 

 lies deeper than in the previously discussed sections. 

 The minimum is not very pronounced, the lowest values 

 being higher than 34.5 per mille. The axis of the lowest 

 values is found at approximately 900 meters where the 

 temperature is about 5°. The isotherm of 5° sinks 

 slightly toward the coast but the salinity minimum is not 

 so well defined that the axis of this minimum can be 

 traced with any certainty, for which reason it cannot be 

 seen whether or not this axis deviates from the horizon- 

 tal direction. The deep water is again very uniform with 

 a temperature which decreases slowly with increasing 

 depth and a salinity which increases slowly. 



