46 THE OCEANOGRAPHY OF THE NORTH-WESTERN OCEAN [PART I 



the Atlantic from the surface to the bottom is filled with water 

 which is relatively heavy, and a very deep layer from the surface 

 downwards is comparatively high in temperature. But encounter- 

 ing the Scotland-Iceland barrier the lower part of the stream is 

 arrested and only the superficial layers flow on over the colder 

 waters of the Norwegian Sea. Just such another barrier exists in 

 the barrier which is present at the Straits of Gibraltar. This 

 rises to comparatively near the surface and arrests the flow of 

 Atlantic water of deep origin. Only superficial Atlantic water 

 enters the Mediterranean, flowing over an undercurrent of warm 

 water which passes out into the Atlantic. Down to great depths 

 the temperature in the former is 12° C. to 13^ C 



A glance at the chart on p. 47 will shew the further course of 

 the European Stream. This is the first chart which was con- 

 structed from simultaneous salinity observations in the Atlantic, 

 the North and Norwegian seas, and it appears that it is not quite 

 typical of the conditions usually occurring. It shews that Atlantic 

 water enters the Norwegian Sea over all the banks between 

 Shetland and Iceland. It is the case that the stream flows as 

 a very general rule only through the Faeroe Shetland Channel. 

 In 1896 we have what is apparently a maximum extension of the 

 Atlantic flooding of the Northern Ocean. It will be seen that warm 

 and high-salinity water covers a large portion of the Norwegian 

 Sea. It has encroached on the ice barriers round Greenland and 

 Spitzbergen; has flooded the western entrance to the Denmark 

 Strait ; and finally loses itself in the Arctic ocean as far north as 

 Lat. TS'', and as f^ir east as Long. 50°. It has entered the North 

 Sea as a surface currentj and the Baltic as an undercurrent. 



Now remember that the area covered with the waters of the 

 Gulf Stream undergoes periodic expansion and contraction varying 

 between 45° and 50° N. Lat. and that water of comparatively high 

 salinity and temperature must be banked up in the Atlantic 

 Ocean at these latitudes, displacing water which was previously 

 there. Remember too that this gigantic pulsation of the Gulf 

 Stream occurs once a year ; that the maximum expansion of the 

 eddy occurs in November and minimum contraction in March. It 

 must follow from these conditions that the volume of the European 

 Stream, which depends on the banking up in the Atlantic of water 



