THE PACIFIC OCEAN 



91 



The surface salinity (fig. 222; I-B) shows a less 

 symmetrical distribution than the temperature. Two 

 maxima of salinity are found, one in the Southern, and 

 one in the Northern Hemisphere. The former has its 

 center in the eastern part of the ocean in approximately 

 latitude 20° south and longitude 120° west, whereas the 

 latter has its center in the western part of the ocean in 

 approximately latitude 25° north and longitude 175° east. 

 These two areas of high salinity are separated by a 

 narrow belt of low salinity in about latitude 10° north, 

 the lowest salinities occurring in the eastern part of the 

 ocean. Near Central America the salinities are very 

 low, probably because of local conditions. To the north 

 and the south of the areas of high salinity, the surface 

 salinity decreases toward the poles. This decrease ap- 

 pears to be greater in the Northern Hemisphere, where 

 salinities approaching 32.5 per mille are found in the 

 inner part of the Gulf of Alaska and to the northeast of 

 Japan. 



The chart of the surface salinity by Schott repre- 

 sents approximately mean annual isohalines, but in sev- 

 eral regions the observations on which the mean annual 

 values are based, are distributed unevenly over the year 

 and the actual annual values may, therefore, deviate 

 somewhat from the values of the chart. 



The Carnegie data are smaller than the values by 

 Schott on the whole. Negative differences are found in 

 eighty-seven of one hundred and twenty-eight cases and 

 positive differences in nineteen cases only. As a rule, 

 the differences are small and equal to or smaller than 

 0.3 per mille in ninety-one instances. The mean of alt 

 is -0.17 per mille. 



Within the equatorial region no relation exists be- 

 tween the simultaneous deviation from the mean values 

 of temperature and salinity. This becomes evident when 

 plotting the corresponding values in a temperature- 

 salinity diagram, and is also evident from table 7, which 

 contains the corresponding average values for certain 

 regions. Outside the equatorial regions, on the other 

 hand, we find a distinct relation between the correspond- 

 ing deviations: on the average a high temperature cor- 

 responds to a high salinity, and vice versa. This is seen 

 when plotting the corresponding deviations and is also 

 evident from table 7 where, within the three areas out- 

 side the equatorial regions, we find for values of t, l.°5, 

 2.°0, and 3.°6 and the values of S are -0.34, -0.20, and 

 + 0.01 per mille, respectively. 



An increase of 1° in the temperature deviation thus 

 appears to correspond to an increase of 0.15 per mille 

 in the salinity deviation. This increase corresponds to 

 the normal temperature-salinity relation which is found 

 in the Pacific. The relation found between the deviations 

 from the chart values, thus can be interpreted to indi- 

 cate either that the annual variations in temperature and 

 salinity are parallel to one another, or that part of the 

 temperature deviations have nothing to do with the an- 

 nual variation of temperature but are caused by changes 

 in the currents and, therefore, are accompanied by par- 

 allel variations in salinity. At present it is impossible 

 to decide which of these factors is of the greater impor- 

 tance. 



One hundred^neter level . — At this level the temper- 

 ature distribution (fig. 211; I-B) is already materially 

 changed and the difference between the conditions in the 

 eastern and western parts of the ocean is much more 

 pronounced. Here we find a temperature of 12° off Cal- 

 lao, which increases as one proceeds toward the west, 



reaching 20° at the meridian of 100° west, whereas at 

 the surface the corresponding temperatures are 18° and 

 23°. Off San Francisco we find a temperature of 9° in- 

 creasing to 14° at the meridian of 140° west, whereas 

 the corresponding surface values are 13° and 16°. The 

 most conspicuous feature, however, is that north of the 

 equator in about latitude 10° north and longitude 140° 

 west a temperature of 11° is found where the surface 

 value is about 24°. 



Comparingthe Carnegie observations at 100 meters 

 with the values by Schott and Schu, we find deviations 

 of a less systematic character than it the surface. 

 Within wide areas the deviations are sma'l and of chang- 

 ing sign, the mean of all being 0°37. Deviations greater 

 than 5° are found off Japan, to the south of Bering Sea, 

 and to the north of the equator between the parallels of 

 5° and 15° north, in the region of the Equatorial Counter- 

 current. 



The Schott-Schu chart shows a belt of tempera- 

 tures below 20° stretching across the ocean in about 

 latitude 10° north and separating the warm water mass- 

 es of the two hemispheres. In the figure this belt of low 

 temperatures is shown in the eastern part of the ocean 

 only, but it must be admitted that in the western part the 

 distances between the stations are so great that the fea- 

 ture may have escaped observation. 



The seasonal variation of temperature due to the 

 influence of heating and cooling is probably very small 

 at the 100-meter level (Helland-Hansen, 1930). The dif- 

 ference, therefore, cannot be ascribed to such seasonal 

 variations, but must be related to changes in the currents. 

 These changes may be of an accidental or periodic 

 character and influence both temperature and salinity 

 distribution. We have no means of examining corre- 

 sponding temperature and salinity deviation, but the 

 fact that the greatest differences in temperature occur 

 in regions where strong and varying currents prevail, 

 indicates that the discrepancies are owing to displace- 

 ment of these currents. 



The distribution of the salinity at the 100-meter 

 level (fig. 223:1-B) shows the same features as at the 

 surface, but the difference between the western and 

 eastern part of the ocean is more pronounced. Very low 

 salinities are found off the Peruvian and Californian 

 coasts. The minimum north of the equator is less pro- 

 nounced. 



Two hundred-meter level . --The temperature dis- 

 tribution (fig. 212; I-B) shows a new and interesting fea- 

 ture. At this level the belt of low temperatures to the 

 north of the equator can be followed across the ocean as 

 far as the observr^tions are extended, md a similar belt 

 appears to be present directly to the south of the equa- 

 tor, whereas higher temperatures prevail at the equator. 



The typical region of low temperature, which at 

 higher levels could be followed from the coast of Peru 

 toward the west along the equator, has now moved to the 

 south and is found entirely in the Southern Hemisphere. 



In the Schott-Schu chart only one belt of low tem- 

 peratures to the north of the equator is seen, -the second 

 belt to the south of the equator is not present. It is pos- 

 sible that the existence of the two belts is connected 

 with the special development of the currents at thr time 

 when the Carnegie observations were made, but even if 

 this is the case, the feature is characteristic of the con- 

 ditions in the central Pacific. 



The average discrepancy between the Carnegie ob- 

 servations and the corresponding values according to 



