176 WATER MASSES AND CURRENTS OF THE OCEANS 



No velocities are entered on the figure, but within the Norwegian 

 Current velocities up to 30 cm/sec, or about 0.6 knots, occur, and within 

 the East Greenland Current, where the water moves fastest directly 

 off the shelf, velocities of 25 to 35 cm/sec are encountered. These 

 values are based partly upon computation from the distribution of density 

 and partly upon direct current measurements. 



In the North Sea a counterclockwise circulation is also present, as 

 has been demonstrated not only by the distribution of temperature and 

 salinity but also by the results of large-scale experiments with drift 

 bottles. The details of the currents are much more complicated than is 

 shown in the figure, and several smaller but permanent eddies appear to 

 be present. In the straits between Sweden and Denmark the surface 

 current is directed in general from the Baltic to the North Sea, but along 

 the bottom the water flows into the Baltic. In the Baltic and the adja- 

 cent gulfs the currents are so much governed by local wind conditions 

 that no generalization is possible. 



In the North Polar Sea the surface currents are also greatly influenced 

 by local winds. An independent current appears to be present only to 

 the north of Spitsbergen and to the northeast of Greenland, where the 

 surface waters flow south, feeding the East Greenland Arctic Current. 

 The greater part of the Atlantic water that reaches Spitsbergen as the 

 northern branch of the Norwegian Current submerges below the Arctic 

 surface water and spreads as a warm intermediate layer over large parts 

 of the Polar Sea. 



In the Barents Sea a counterclockwise circulation prevails, with rela- 

 tively warm water of Atlantic origin on the southern side and Arctic 

 water on the northern, and with numerous eddies in the central portion. 

 In the other marginal areas of the Polar Sea, the Kara Sea, the Laptev 

 Sea, the North Siberian Sea, and the Chukotsk Sea, the currents are 

 mainly determined by local winds and, in summer, by the discharge of 

 large quantities of fresh water from the Siberian rivers or the Yukon 

 River, but details of the currents are little known. 



The Norwegian Current and its branches are subject to variations 

 that are related to other phenomena. Helland-Hansen found that in 

 1929 the Atlantic water flowing into the Norwegian Sea was not only 

 warmer and of higher salinity but that the volume was also greater. He 

 points out that such an increased inflow must have had far-reaching con- 

 sequences. Owing to the time used by the water to reach the Barents 

 Sea, the effect of the large amount of warm water should have appeared 

 in the Barents Sea two years after the water was observed off southwestern 

 Norway, and the inflow of warmer water should have led to an increase 

 of the ice-free areas in spring. In agreement with this reasoning the ice- 

 free areas in the Barents Sea east of 20°E in May, 1929, comprised 330 

 km^, and in May, 1931, they comprised 710 km^. The causes of such 



