100 



OBSERVATIONS AND RESULTS IN PHYSICAL OCEANOGRAPHY 



water which has a salinity of 34.00 per mille has a tem- 

 perature of about 3°, and water having a temperature of 

 6° has a salinity which is smaller than 33.5 per mille. 



The deep water is again of a uniform character, but 

 appears to be somewhat cooler than the deep w-ter at 

 corresponding depths in the equatorial region. Thus the 

 isotherm of 2° lies at a depth of about 1700 meters in 

 Section XVI, but at the equator it lies at a depth of about 

 2300 meters. The salinity of the deep water appears to 

 be smaller than in the most northern region; the depth 

 of the isohaline, 34.6 per mille, is about 2300 meters in 

 Section XVI, but at the equator it is about 1600 meters. 



Distribution of Density 



The horizontal and vertical distributions of density, 

 t, have been represented in figures 234 to 245; I-B and 

 96, 102, 108, 114, 120, 129, 135, 144, 150, 156, 162, 168, 

 174, 180, 189, and 198; I-B, respectively. When prepar- 

 ing these the course of the isotherms and isohalines was 

 taken into account. We shall not enter into details but 

 only draw attention to the most prominent features. 



When examining the figures showing the horizontal 

 distribution, it should be borne in mind that at any level 

 the movement of the water, relative to the direct'y under- 

 lying water, takes place in such a direction that in the 

 Northern Hemisphere one has the light water on the 

 right-hand side, and in the Southern Hemisphere the 

 light water on the left-hand side. 



Surface. --Here we find the lowest densities on both 

 sides of the equator in low latitudes. The be'ts of low 

 density are separated from each other by a region of 

 higher density where, however, the values are only a 

 little above the values to the north and to the south. To 

 the north of the region of low density in the Northern 

 Hemisphere the density increases rapidly with increas- 

 ing latitude. This increase is regular except in the re- 

 gion off the coast of California and at the coast of Japan. 

 In the Southern Hemisphei e the density appears to in- 

 crease toward the coast of South America and toward the 

 south, but within a great area off the coast of South 

 America the density remains practically constant. Along 

 the coast of Central America the surface density is very 

 small within a limited region. 



One hundred-meter level. --At this level the region 

 with minimum density to the north of the equator partly 

 has been replaced by a region of very high density. To 

 the north of latitude 20° north the density increases to- 

 ward the north except in the region off the coast of Cali- 

 fornia where a rapid increase toward the coast takes 

 place, whereas the densities are low off the southern 

 coast of Japan. In the Southern Hemisphere the increase 

 toward the coast of South America and toward the south 

 are the most conspicuous features. The low densities 

 along the coast of Central America have disappeared. 



Two hundred-meter level. --Here the development 

 has continued in the same direction. The region of max- 

 imum density to the north of the equator, however, is 

 less pronounced but stretches across the ocean. Tv;o 

 regions of minimum density are under development in 

 latitudes 20° north and 17° south, and from the former 

 there is a general increase toward the north and toward 

 the coast of California. The low densities off the south- 

 ern coast of Japan are stilt conspicuous. In the Southern 

 Hemisphere the increase of density toward the south is 

 more prominent than the increase toward the coast of 

 South America. 



Three hundred-meter level .--Here the high densities 

 in the equatorial region show a stripe-like distribution. 

 The density minimum in latitude 20° north is the domi- 

 nant feature in the Northern Hemisphere. A correspond- 

 ing minimum is probably developed in the same lat'tude 

 in the Southern Hemisphere, but the observations are 

 not extended over a sufficiently wide area to show the 

 entire minimum. 



Four hundred- and five hundred-meter 'evels". --At 

 these levels we find practica'ly the same distribution as 

 at the 300-meter level. An ai'ea of high density covers 

 the equatorial region to almost 20° south and 20° north, 

 and the stripe-like distribution is still seen. In the 

 Northern Hemisphere the minimum is being displaced 

 more and more toward the north. At these levels and at 

 the 300-meter 'evel the 'ow density off the southern . 

 coast of Japan still prevails. 



Seven hundred-meter 'evel. --Here the distribution 

 in the Northern Hemisphere is the same as before, ex- 

 cept that the minimum has shifted farther north, but in 

 the Southern Hemisphere we find a decrease of the den- 

 sity toward the south .nt the most souther'y stations. At 

 these stations the direction of the relative current thus 

 seems to be reversed. Above the 700-meter level the 

 relative current is directed toward the coast; below the 

 700-meter level it appears to be directed away from the 

 coast. 



One thousand-meter level. --The differences in den- 

 sity have decreased regularly downward and at this 'evel 

 are very small, but in the Northern Hemisphere thedis- 

 tribution h?£ remained more or less unaltered. In the 

 Southern Hemisphere the decrease of the density toward 

 the south at the most southern stations is more pro- 

 nounced than at the 700-meter level. In latitude 20° 

 south we find increasing density toward the south, where- 

 as at the higher levels we found decreasing densities. 

 The relative current, which at the higher levels was di- 

 rected toward the west, appears at this level to be di- 

 rected toward the east. 



Fifteen hundred-meter level. --Here the differences 

 in density are very small between latitudes 40° south and 

 and 40° north, but to the north of 40° north we find, even 

 at this level, an increase toward the north. This indi- 

 cates a relative movement toward the east as in the up- 

 per layers. At the southern stations off South America, 

 on the other hand, we still find a decrease toward the south, 

 j which indicates relative movement toward the west. 



Two thousand-, twenty-five hundred-, and three 

 thousand-meter levels. --Here the density is near'y con- 

 stant but the values appear to be lower in the Northern 

 than in the Southern Hemisphere. 



We shall not enter on a discussion of the distribution 

 of th-e density in the vertical sections because such a 

 discussion would not add materially to the knowledge of 

 the character of the different water masses which has 

 been obtained by a discussion of the distribution of tem- 

 perature and salinity. 



Temperature-Salinity (tS) Relation 



The temperature-salinity diagrams for each station 

 in the Pacific are shown in figures 203 to 209; I-B. We 

 shall not enter on any detailed discussion of the charac- 

 teristic features of these diagrams at the single stations 

 but shall make use of the tS relation in order to point out 

 the characteristic properties of the water at different 

 levels and in different regions. 



