THE PACIFIC OCEAN 



97 



which changes from southwest to west -southwest. The 

 eastern part of this section off the American coast has 

 already been discussed because stations 130 to 134 were 

 used when construction Section V. 



The convection layer is thin at all the stations of the 

 section, remaining, as a rule, thinner than 40 meters. 

 Water of a temperature higher than 25° is found directly 

 below the surface to the west of station 136. Below the 

 warm surface layer the temperature decreases rapidly 

 with increasing depth. The isotherm of 10° is met with 

 at a depth of almost 400 meters at station 140: it rises 

 slowly when approaching the American coast, and direct- 

 ly off the coast a rapid rise takes place, indicating an 

 accumulation of cold water. 



The low surface salinities off the coast have already 

 been discussed. Proceeding toward the west, we find in- 

 creasing surface salinities and values above 35.00 per 

 mille at stations 137 to 140. The lowest salinities in 

 this region are found at a depth of about 400 meters 

 where the values lie between 34.00 and 34.1 per mille. 

 The axis of the salinity minimum in the western part of 

 the section shows minor bends up and down and follows, 

 on the whole, the isotherm of 8°, which also oscillates 

 up and down in a corresponding manner. The axis rises 

 when approaching the coast, and we can regard it as fol- 

 lowing practically the same isotherm to the coast if, in 

 the region where the salinity decreases with increasing 

 depth, we take the value 33.95 per mille as the charac- 

 teristic value of this intermediate water. The feature 

 which should especially be emphasized is that between 

 stations 136 and 140 this intermediate water has a salin- 

 ity above 34.00 per mille and a temperature of 8° and is 

 found at a level of 400 meters. The rise of the interme- 

 diate water as it approaches the coast should also be 

 borne in mind. 



The deep water, as previously, shows a nearly uni- 

 form temperature which decreases toward the bottom. 

 The variations in a horizontal direction are small and 

 appear to have an irregular character. The salinity in- 

 creases slowly with depth and at the 2000-meter level 

 no differences in a horizontal direction are perceptible. 



Section XV. --Section XV (stations 142 to 146) repre- 

 sents a very short section which runs east and west in 

 approximately latitude 33°. The convection layer again 

 has a thickness of less than 40 meters. The isotherms 

 are almost horizontal and the temperature decreases to 

 less than 10° within the upper 300 or 400 meters. 



The surface salinity is lower than 35.00 per mille at 

 all stations except 144, and the salinity decreases with 

 increasing depth. In the eastern part of the section sev- 

 eral irregularities, intermediate minima and maxima, 

 occur which indicate more or less complicated currents. 

 A very pronounced salinity minimum with values below 

 34.00 per mille is shown at all stations. The axis of the 

 lowest value rises considerably from west to east, lying 

 at a depth of about 600 meters at station 142 and at a 

 depth of 550 meters at station 146. It follows almost 

 exactly the isotherm of 7° running slightly below this 

 isotherm to the west of station 144 and slightly above 

 this isotherm to the east of station 145. 



Comparing the characteristics of this intermediate 

 water with those of the corresponding water at stations 

 136 to 139 of the preceding section which lies about 10° 

 farther south, we find that the layer of water of low sa- 

 linity rises toward the south and that the salinity and the 

 temperature of this water increase together. In both 

 sections we find the intermediate water at a lower level 



when the distance from the American Continent is great- 

 est. 



Section VI. - -Section VI, comprising stations 125 to 

 130, runs from latitude 51° 58' north, longitude 150° 39' 

 west to San Francisco. The convection layer is thin and 

 reaches a thickness of more than 50 meters at station 

 129 only. The surface temperature increases as one 

 proceeds to the southeast, and remains practically con- 

 stant from station 128 to the coast. The decrease of 

 temperature with increasing depth is rapid in the most 

 northern part, especially at station 125 where tempera- 

 tures higher than 6° are found above 45 meters only. 

 The high surface temperatures in this region appear to 

 be the result of heating in summer. On the whole, the 

 subsurface temperature increases toward the southeast 

 as shown by the sinking of the isotherms in this direc- 

 tion. Down to a depth of about 300 meters between sta- 

 tions 129 and 130, however, the isotherms rise, indicat- 

 ing the accumulation of cold water at the coast. The 

 observations at stations 129 and 131, combined with the 

 data from station 130, thus reyeal the same features. 

 The sinking of the isotherm of 5° is, on the other hand, 

 especially rapid between stations 129 and 130, suggesting 

 a downward motion of the water at a depth of about 600 

 meters. A corresponding divergence of the isotherms 

 was found between stations 68 and 71 off the coast of 

 South America. 



The surface salinities are very low at all stations, 

 being less than 33.00 per mille in the northwestern part 

 of the section. A rapid increase takes place at a depth 

 of about 150 meters and below this depth the salinity in- 

 creases more slowly. It is noteworthy that the increase 

 with depth is slow at a level of about 500 meters except 

 at the most northwestern stations. The value of the sa- 

 linity in the interval having slow increase is between 

 33.9 and 34.1 per mille, and the temperature ranges 

 from 7° to 3.°5 at station 127, and from 8° to 6° at sta- 

 tion 130. It is probable that at this depth we find the 

 water, which, in the more southerly sections, represents 

 the intermediate water. Between stations 129 and 130 

 the isohalines rise at all levels and thus give no indica- 

 tion of a downward movement at a level of 500 meters as 

 suggested by the course of the isotherms at this layer. 



The deep water appears to be very uniform. The'2° 

 isotherni runs practically horizontally at a level of 2000 

 meters, and at this depth a uniform salinity of slightly 

 more than 34.6 per mille is found. 



After this brief description of the vertical distribu- 

 tion of temperature and salinity in the eastern part of the 

 North Pacific, we turn to the conditions in the western 

 part. 



Section Vin. - -Section VHI (stations 94 to 104) runs 

 mainly in a southeasterly direction from latitude 20° 12' 

 north, longitude 161° 19' east to the Samoan Islands. The 

 section thus crosses the equator and, therefore, shows a 

 number of features which are similar to those in the 

 southern part of Section V. When examining the section 

 it must be borne in mind that the northern part runs al- 

 most from'east to west and variations which are charac- 

 teristic for the north-south direction, therefore, appear 

 much exaggerated in our representation. This is evident 

 from figures 32 and 33, for instance, in which the obser- 

 vations at stations 95 to 104 have been used for the con- 

 struction of true north and south sections. 



The convection layer has a thickness of 50 meters 

 or more at the northwestern station and reaches almost 

 100 meters at station 99. At station 98, which is located 



