DEEP CURRENTS: ATLANTIC OCEAN 89 



in the South Sandwich deep before continuing eastwards across the Atlantic Ocean. It 

 will be shown in a later part of the report that the water in the northward movement 

 probably contains water from the deep currents of both the Atlantic and Pacific Oceans, 

 and its low temperature and salinity and high oxygen content show that these waters are 

 mixed with a large proportion of the cold deep and bottom waters of the Weddell Sea. 



The observations in section 6 (Plates VIII, IX) indicate that the northward move- 

 ment is strongest at St. 1140, very near the South Sandwich Islands and the south- 

 ward movement at St. 1142 in 20 31' W in the eastern half of the South Sandwich 

 deep. Section 5 (Plates VII, IX), a longitudinal section in the eastern part of the deep, 

 also shows that there is a strong southward movement ; at St. 806 in 57-J S the water 

 between 800 and 1000 m. has a salinity of as much as 34 - 76-34*75 °/ 00 , and it must be 

 largely Atlantic water. The deep water at St. 808 also has a relatively high salinity and 

 temperature, and it seems that the Atlantic water reaches as far as 6o° S. 



Between St. 806 and 808 the deep water has a lower temperature and salinity, and a 

 higher oxygen content, and the data in the section suggest that there is a sharp cyclonic 

 current eddy in which the relatively cold deep water belonging to the northward current 

 along the Scotia Arc is carried eastwards into a region where the Atlantic water might other- 

 wise flow southwards without interruption. The eddy appears to be a permanent feature 

 of the water movements in this region ; it is shown in a section constructed by Mosby 

 (1934, fig. 14), affecting the conditions at Norvegia St. 48 between St. WS 555 (Station 

 List, 1932) and 'Vikingeri' Sts. 1 and 2 (Ruud, 1930); it is probably caused by the in- 

 fluence of some irregularity of the bottom topography which has not yet been discovered. 



Sections 5 and 6 both show that the temperature of the warm deep water decreases 

 suddenly towards the south in about 6o° S, and between the warm deep water found 

 north of this latitude and a further warm region near the Antarctic Continent, the deep 

 water is so cold that it can only belong to an eastward movement of deep and bottom 

 waters from the Weddell Sea. Against this cold current, which cannot contain any 

 appreciable volume of Atlantic water, the southward movement of the North Atlantic 

 deep water comes to an abrupt end. The data available are sufficient to show that the 

 cold current is continuous towards the east as far as 30 E, but it is not certain that the 

 Atlantic current throughout the whole of this distance has such a sharp termination as 

 it has east of the South Sandwich Islands. The sudden difference of temperature in the 

 deep layer between Sts. 460 and 461 (Station List, 1932), and the abrupt change of 

 salinity between St. 453 (ibid.) and Norvegia Sts. 1-3 (Mosby, 1934) show, however, 

 that there is probably a sharp boundary lying a short distance south of Bouvet Island. 

 The observations in section 7 (Plates X-XII), in about 15 E, are too far apart to show 

 whether the Atlantic current has a sharp termination ; the deep water at St. 1 160, how- 

 ever, seems to be plainly Atlantic water, whilst that at St. 11 58 belongs to the eastward 

 current from the Weddell Sea, and the section suggests that the Atlantic water reaches 

 as far as 55— 56 S. 1 



1 The origin of the deep water at St. 1147 (section 6) in 61° 50' S, 8 :> 10' W, is not quite certain, but on the 

 whole the data suggest that it belongs to the warm deep current found near the Antarctic Continent (see p. 93). 



