APPENDIX B : HELLAND-HANSEN — 4 — 



in the figures by trebly crossed lines, indicating water of higher salinity than 3 5 '2 5 °/oo. 

 The Stream enters the Channel from the Atlantic in a direction varying between north- 

 east and south-east, and when in the Channel, follows a more northerly course 

 along the Shetland bank. In August 1903 , the Stream came along the southern 

 section, so that Fig. 4 gives partly a longitudinal section through the Stream whilst the 

 other figures are cross-sections. In 1902 and 1903, the Stream was limited as a rule to 

 the eastern half of the Channel in the neigbourhood of the Shetland Isles, which may 

 have been quite surrounded by the strongly saline Atlantic water. From time to time, 

 indeed, the Stream fills almost the whole surface of the Channel between the Fseroes 

 and the Shetlands; but these are obviously only exceptional cases. The depth of the 

 water which streams through the Channel into the Norwegian Sea, can in general be 

 placed at 5 — 600 m.; the relatively unmixed Atlantic water, with a saUnity of over 35-2 <;°/oo, 

 has a depth varying between 200 and 500 m. With the help of V. Bjerknes' dynamic 

 theory, numerous approximations have been calculated for the rapidity of the Stream's 

 flow ^ These calculations have given the following results amongst others : in August 

 1902, the average rapidity on the surface was about 10 sea-miles per 24 hours (0-2 m. per 

 second); in December of the same year, it was probably a Httle less; in May 1903, it 

 was about 15 sea-miles (0-3 m. per second) and again about 10 s. m. in the following 

 August. The rapidity of flow varies but little in the upper few hundred meters; some- 

 times the greatest rapidity of flow is at a depth of about 100 m. Great masses of water 

 are therefore carried by the Stream into the Norwegian Sea. An attempt to calculate 

 this quantity for August 1902 gave 4,000,000 m3 per second. 



The Atlantic Stream send off'shoots into the North Sea, partly through the opening 

 between Scotland and Shetland, partly round the north of Shetland. A distinct periodicity 

 occurs in this inflow of Atlantic ocean-water into the North Sea. It has long been 

 known, that the northern North Sea plateau (north of the Dogger Bank) was covered 

 by water of very high salinity, which in summer had a temperature as low as ca. 7° C. ; 

 the true North Sea water of lower salinity lies above this bottom-water as a layer 

 40 — 60 m. thick. The temperature remains almost the same throughout the whole year, 

 but was a little higher in December 1902 than, for example, in August. Regular obser- 

 vations have now shown, that this North Sea bottom-water is of Atlantic origin and 

 that if comes into the North Sea almost exclusively in the winter half-year. In December 

 1902, it began, as a branch of the Atlantic Stream, to pour into the North Sea round 

 the north of Shetland; later, in the first months of 1903, it possibly came mainl}' to the 

 south of Shetland. The Atlantic water was then cooled down in the North Sea during 

 the cold period of the year; in winter, the temperature at the oottom is a little higher 

 than in summer, as the minimum spreads but slowly down into the depths. This water 

 remains for the most part in the North Sea throughout the whole summer until the 

 next winter; its movements in all probability are but slow. The same conditions are 

 probably repeated regularly and not restricted to the two years spoken of here. The low 

 bottom-temperature occasionally found in summer by earlier investigations speak in 

 favour of this. The reason why the inflow of the Atlantic ocean-water through the 



I) According to the method, described in Sandström and Helland-Hansen's paper; Ueber 

 die Berechnung von Meeresströmungen (Report on Norwegian Fishery and Marine Investigations. II. 

 4. 1903.) 



