BJØRN HELLAND-HANSEN AND FRIDTJOF NANSEN. M.-N. Kl. 



tween his Section II and his Section VIII. The distance between them 

 being about 230 nautical miles, the decrease is about 0.035 "/00 i" 10° 

 miles. It seems probable that in the northern regions, where the Atlantic 

 water is covered by a surface-layer with low salinities and also by ice a 

 great part of the year, the decrease in the salinity of the Atlantic water is 

 comparatively slow, because the much lighter surface-layer (as also the ice) 

 is a hindrance to a deep vertical circulation during the winter, which is 

 otherwise an important factor in the intermixture of the underlying 

 water with the less saline surface-water. 



At the Belgica-Station 23 (in 77" 25' N. Lat., 4^3' W. Long.) in 

 the westward branch of the Spitsbergen Atlantic Current, there was a 

 maximum salinity of 35.00 "/00 in 100 metres. [Due D'Orléans, 1907, 

 p. 190]. The distance travelled by this Atlantic water was probably nearly 

 the same between the region of Isachsen's Sect. II and this place, as be- 

 tween his Sections II and XHII. The decrease of the salinity was the same 

 in both cases. 



All these observations consequently agree fairly well, and we have 

 thus been able to trace approximatel}' the regular changes in the salinity 

 of the waters of the Spitsbergen Atlantic Current on their way northwards 

 and westwards. 



Srasoiiaf ]\iriatioiis in the Salinity. 



The observations of June, July, and September, at Stats. 3, 4, 29, 30, 

 and 31, indicate the regular decrease in the salinity of the surface-layers 

 during the summer, which occurs more or less in most parts of the 

 North Atlantic and the Norwegian Sea, and is especially striking in the 

 Arctic regions. This reduction of the salinity is due to several causes. 

 B}' the heating during the summer and the increased admixture of 

 river-water from land, in the warm season when the snow melts, the 

 coast-waters become much lighter, and will spread much farther seawards 

 than in the winter, when they become heavier by cooling (and in the Arctic 

 regions also by the formation of ice, increasing the salinit}'). Owing to the 

 deflecting effect of the Earth's rotation, they will therefore, in the winter, be 

 forced nearer to the coasts to the right of the current. In the Arctic regions 

 the waters carried by the Arctic and Polar currents are of the same nature 

 as the coast-waters. The salinit}' of their surface-layers is much reduced by 

 the melting of the floating ice during the warm season, while their salinity 

 is increased during the cold season by the formation of ice on the surface. 

 These waters will consequently have a tendency to spread over wider 

 areas in the summer and autumn than in the winter and spring. 



