102 



OBSERVATIONS AND RESULTS IN PHYSICAL OCEANOGRAPHY 



mille at a temperature of 5°3 and at greater depths 

 increases with decreasing temperature. The minimum 

 value is found above the 400-meter level, and the cor- 

 responding values of temperature and salinity are both 

 lower than the corresponding values in Region 11, but 

 there they are found below 500 meters. 



In Region 14 to the south of the Aleutian Islands and 

 the Bering Sea we find increasing temperature with de- 

 creasing salinity up to 500 meters, but above this level 

 the temperature remains constant at about 3°4, whereas 

 the salinity decreases. 



It is seen that the tS curves in regions 1 and 2 and 

 regions 10 and 11 have nearly the same form except in 

 Region 1 near the surface. The stratification is thus of 

 a similar character in the North and South Pacific. The 

 transition from the tS curve in about latitudes 40° south 

 and 40° north to the tS curves of the equatorial region is 

 more or less similar in both hemispheres. 



The Intermediate Water 



The most conspicuous feature which is revealed by 

 the curves is the existence of water of low salinity at an 

 intermediate depth. In the Southern Hemisphere the in- 

 termediate water of the Pacific Ocean is probably being 

 formed in the same manner as the corresponding inter- 

 mediate water of the Atlantic and Indian oceans; it sinks 

 and flows north from the region of the Antarctic conver- 

 gence, which has been traced all the way around the 

 Antarctic Continent. 



If the Antarctic intermediate water follows a more 

 or less direct course from the region where it sub- 

 merges to the regions in which we have found it, we 

 must assume that the water has a high oxygen content. 

 Fortunately the oxygen content has been observed at two 

 of the Carnegie stations in regions 1 and 2, namely at 

 stations 52 and 57. At station 52 the observations show 

 a maximum of oxygen, 5.09 ml/L, at a depth of 657 me- 

 ters where the intermediate water was found. At sta- 

 tion 57 observations are lacking for the central part of 

 the intermediate water but at the upper part of this 

 water, at a depth of 468 meters, the oxygen content 

 showed a maximum of 5.47 ml/L. Thus, the intermedi- 

 ate water appears to have a high oxygen content in con- 

 trast with the corresponding water in the Northern 

 Hemisphere. This high content strongly supports the 

 opinion that the water comes on a direct route from a 

 region where it has been in contact with the atmosphere. 



In the Northern Hemisphere a convergence, corre- 

 sponding to the Antarctic convergence, is not found, but 

 we have seen, when studying Section DC, that big whirls 

 are formed along the boundary of the warm and the cold 

 water off the Japanese coast, and it was pointed out that 

 within these whirls water of the typical properties of the 

 intermediate water was found. In this region probably 

 we must look for one of the places where a supply of 

 water to the intermediate current takes place. It is 

 possible that the region where such whirls are formed 

 extends to some distance from the Japanese coast, but 

 this extension cannot be very great, considering the 

 general character of the currents. The water which is 

 supplied to the intermediate current should thus be 

 formed by mixing of different water masses in the re- 

 gion off Japan, but this mixing takes place below the 

 surface, judging from the conditions which are repre- 

 sented in Section IX. 



The mixing appears to take place between water of 



low temperature and low salinity coming from the north, 

 perhaps from the upper layers, and warmer water of 

 higher salinity which is carried from the south by sub- 

 surface currents. Therefore, part of the water which 

 supplies the intermediate current has not been in direct 

 contact with the atmosphere and must consequently con- 

 tain a relatively small amount of oxygen. Such process- 

 es would explain the fact that the oxygen content of the 

 intermediate water in Region 11 is of the order of be- 

 tween 2 and 4 ml/L. In this reg'on the oxygen content of 

 the intermediate water generally decreases with in- 

 creasing depth, but a secondary maximum between 300 

 and 400 meters at stations north of latitude 20° north in 

 indicates an admixture of surface water. 



The Deep Water 



Temperature and salinity. --When discussing the 

 horizontal and vertical distribution of temperature and 

 salinity, we pointed out that the deep water is of a very 

 uniform character. The temperature lies between l.°5 

 and 2°, and the corrected salinity between 34.65 ?nd 

 34.73 per mille. Our horizontal representations went 

 down to a level of 3000 meters. It is of interest to ex- 

 amine the few observations which are available for 

 greater depths. At several stations observations with 

 intervals of about 500 meters were taken below the 3000- 

 meter level. At a great number of stations the tempera- 

 ture at the bottom was measured, but in these cases no 

 water samples were obtained for determining the salin- 

 ity. 



Table 9 gives the mean temperatures and salinities 

 within the regions into which the ocean was divided on 

 the basis of the tS relations. The mean values have been 

 computed for the intervals 3000 to 3500, 3500 to 4000, 

 4000 to 4500, and below 4500 meters. From the last in- 

 terval only temperature observations are available, and 

 from the interval 4000 to 4500 meters salinity observa- 

 tions are present from regions 4 and 6 only. 



It is seen that the temperature is very uniform in 

 the great depths of the North Pacific where the greatest 

 difference between any of the mean values from the dif- 

 ferent depths and different regions amounts to only 0.°24. 

 The temperature appears to increase slightly toward the 

 bottom within some of the regions and later we shall re- 

 turn to this feature. 



In the South Pacific we find, on the other hand, con- 

 siderable variations both in a horizontal direction and 

 with depth. The highest temperature is found in Region 

 6 near the equator off the coast of South America and off 

 the coast of Peru where the temperature is constant 

 between 3000 and 4000 meters. In Region 5 in the cen- 

 tral part of the Pacific in latitude 15° south and in the 

 most southern region--l--the temperature decreases 

 with increasing depth. 



The salinity appears to decrease from the Southern 

 to the Northern Hemisphere but within each region the 

 variations in a vertical direction are so small that they 

 are within the limits of the accuracy of the observations. 

 The values in the table should probably be increased by 

 0.03 per mille (see p. 72). 



Bottom temperature. --The bottom temperatures at 

 depths greater than 3000 meters have been entered in 

 table 10 and figure 21. The values underscored in the 

 figure refer to depths between 3000 and 4000 meters. In 

 the South Pacific high bottom temperatures are found in 

 the eastern part but here no observations from depths 



