84 



OBSERVATIONS AND RESULTS IN PHYSICAL OCEANOGRAPHY 



At station 9, to the southwest of Iceland, water of a 

 relatively high temperature and salinity was still found, 

 but at stations 10 and 11 low temperatures were present 

 below a depth of 75 or 100 meters, and salinities above 

 35 per mille occurred only at some leve's above 200 

 meters. 



At station 12 the temperature was still lower, name- 

 ly 3.°60 at 75 meters, decreasing to 3°30 at 500, 3.°10 at 

 1000, and 2.° 75 at 2000 meters, whereas the salinity re- 

 mained practically constant and equal to 34.87 per mille, 

 perhaps increasing slowly with depth below 500 meters. 

 The density in situ was almost constant between 75 and 

 100 meters, varying between 27.74 and 27.77, but below 

 700 meters it increased slowly to 27.86 at 2500 meters. 



The uniform character of the water in the region of 

 station 12 has been pointed out by r.Tatthews and consid- 

 ered by Jacobsen (1929), who especially discussed the 

 opinion of Nansen regarding the origin of the deep water 

 of the Western Atlantic Basin. Nansen had indicated that 

 the region southeast of Greenland is a place where this 

 deep water is formed, because cooling of the surface 

 layers in winter may give rise to convective currents, 

 which, because of the uniform character of the water, 

 may reach to great depths. Jacobsen, however, arrives 

 at the result that these processes probably contribute to 

 the formation of the uniform water north of the Grand 

 Banks of Newfoundland, whereas the true bottom water 

 comes from the continental shelf in Denmark Strait. 



Vertical Sections 



The most' important results of the work of the Car - 

 negie in the Atlantic are represented in the two vertical 

 sections I and II. Section I is based on the observations 

 at stations 13 to 24 and shows a north and south section 

 approximately along the meridian 40° west between lati- 

 tudes 46° and 8° north. Section II is from the observa- 

 tions at stations 25 to 34 and shows an east and west 

 section approximately along the parallel 12° north and 

 between longitudes 37° and 79° west. 



Section I. --Section I, comprising stations 13 to 24, 

 is taken across the Atlantic Ridge, as is evident from 

 the profile of the bottom. Station 13 is situated on the 

 Grand Banks of Newfoundland; stations 14, 15, and 16 in 

 the Western Atlantic Basin; stations 17 and 18 on the 

 ridge; and the rest of the stations, from 19 to 24, are in 

 the Eastern Basin. 



The isotherms in Section I (fig. 94; I-B) show the 

 well -'mown accumulation of warm water with its center 

 at about latitude 30° north. Considering the rapid vari- 

 ation in temperature with the distance from the Grand 

 Banks, a station on the slope of the Grand Banks would 

 have been of value in order to establish the course of 

 the isotherms. The double bend of the isotherms south 

 of the Grand Banks indicates the existence of a whirl at 

 the boundary between the cold water on the southern 

 slope of the Grand Banks and the warmer water to the 

 south. In this region, but in another location, a similar 

 whirl is indicated bvthe Michael Sars section (Helland- 

 Hansen, 1930), which runs a little to the west of the Car- 

 negie section. It is probable that changing whirls of dif- 

 ferent dimensions are formed at the boundary of the Gulf 

 Stream, for which reason the hydrographic conditions in 

 a given locality may change rapidly. Our section, there-, 

 fore, represents the conditions as observed by the Car - 

 negie , but probably not any stationary conditions. 



The isohalines in Section I (fig. 95: I-B) clearly 

 show the great accumulation of water of high salinity 

 with its center at about latitude 30° north. The isohaline 

 35 per mille reaches, at the center, to a depth of more 

 than 2000 meters. The whirl to the south of the Grand 

 Banks, which was indicated by the temperature distribu- 

 tion, is also shown by the course of the isohalines. 



To the south the influence of the intermediate Ant- 

 arctic Current is seen in the minimum of salinity at a 

 depth between 500 and 1000 meters. The effect of this 

 intermediate current reaches, according to the Carnegie. 

 at least beyond station 20 or to about latitude 20° north, 

 and perhaps can be traced as far as between stations 18 

 and 19; or about latitude 26° north. 



At the surface the greatest salinity is found between 

 stations 18 and 19, or between latitudes 24° and 30° 

 north. From the course of the isohalines, it seems that 

 water of very great salinity is spreading to the north 

 and to the south at a level of about 100 meters. This 

 water represents the type which Jacobsen (1929) has 

 called "central water" in his discussion of the results 

 of the Dana expedition 1920 to 1922. Jacobsen shows, in 

 agreement with the Carnegie results, that at a level of 

 about 100 meters this water is flowing away from the 

 region in which it is being formed, the Sargasso Sea re- 

 gion. 



The deep water appears to have a salinity slightly 

 below 34.90 per mille in both the Western and Eastern 

 basins, but the Carnegie values are probably 0.03 to 

 0.04 per mille too low. 



The density curves in Section I (fig. 96; I-B) show 

 especially that the difference in density between stations 

 15 and 16 reaches a maximum somewhere below the 

 surface. When discussing the conditions at stations 3 

 and 5 (p. 30 and table 1), it was pointed out that the 

 greatest difference in density was found at a depth of 

 about 700 meters. Table 2 is the result of an examina- 

 tion of stations 15 and 16. Here we find a considerable 

 difference in the upper layers, reversal of sign, and a 

 new maximum at about 500 and 700 meters. 



Table 2. Conjparison of values of density, at, 

 at Carnegie stations 15 and 16, 1928 



proximately east and west, following the parallel of 

 about 12° north from 37° to 79° west longitude. It be- 

 gins in the Eastern Basin of the Atlantic in which sta- 

 tions 25 and 26 are located, and continues across the 

 ridge (with station 27 on the ridge), into the Western 

 Basin in which stations 28, 29, and 30 are situated. It 

 then crosses the threshold of the Caribbenn Sea, in 

 which the last four stations--31, 32, 33, and 34--are lo- 

 cated. 



