VII 



PETTERSSON— INTRODUCTORY 



position, that a communication can be established between the Arctic water on 

 the west side and the Norwegian coastal water on the east side of the Atlantic 

 Stream, in such a way that, either the Arctic surface water flows locally at times 

 over the warm Atlantic area in the colder periods of the year, or the Arctic water, 

 as drift -water, presses towards the east underneath the layers of Atlantic water 

 through certain deep channels in the coastal bank e. g. through the Norwegian 

 Channel. This question is not yet decided. Only so much may at present be said 

 with certainty, that the animal and plant life of the plankton and of the bottom, 

 in the eastern boundary-water of the Norwegian Sea and North Sea and in the fjords 

 where such water enters, 

 contains a not inconsiderable 

 number of Arctic and boreal 

 forms. This means, that the 

 Atlantic Stream does not form 

 an absolute barrier between 

 the western and eastern boun- 

 dary-waters of the Norwegian 

 Sea. No evidence has as yet 

 been found by the internatio- 

 nal investigations in favour 

 of the hypothesis, that these 

 organisms are to be regarded 

 as relicts of the glacial period 

 etc. in the Scandinavian 

 seas. 



<vo o>' 



Fig. 5 



It may in general be 

 said, that the Atlantic Stream 



constitutes a boundary — though not an absolute one — between the Arctic water 

 of the Norwegian Sea and the coastal waters of its boundary regions. 



The Norwegian Sea with the Barents Sea comes within the influence of the 

 Atlantic water flowing in between the Fœroes and Scotland. Of the true North 

 Sea: the Norwegian Channel, the Skager Rak and the deep northern plateau as 

 far as the Dogger Bank are directly affected by this influence. The southern shallower 

 North Sea plateau is hydrographically divided from the northern by the Dogger 

 Bank, and receives its contribution of Atlantic water chiefly through the English 

 Channel. The water which enters the North Sea through the deep gut of the 

 Channel, comes from a southern branch of the Atlantic Stream and has a some- 

 what greater salinity and higher temperature than that which enters the northern 

 North Sea round Scotland. Sometimes, the presence of water of lower salinity is 

 detected even at the western end of the Channel, arising probably from coastal 

 water coming from the Irish Channel '. 



At the eastern mouth of the Channel, the Atlantic water remains unmixed 

 only over the depressions between the English and Dutch coasts. On the shallow 



' Donald J. Mathews: Paper read at the 'meeting of the Hydrographical Assistants, July 1903. 



5* 



Northern North 

 Sea plateau 



Scutlicrn Norlli 

 Sea pl.ïteau 



