CH. Il] THE OCEANOGRAPHY OF THE NORTH-WESTERN OCEAN 39 



Thomson Ridge acts as a barrier to the flow of warm water from 

 the Atlantic into the Norwegian Sea, and conversely to the flow 

 of cold water from the Norw^egian Sea into the Atlantic. Fig. 15 

 represents a series of hydrographic soundings on the surface of the 



burPace of the Sea 



De^th 



metres 

 •100 



looo 



Fig. 15. Hydrographic section over the Wyville-Thomson Ridge, in the direction 

 of the axis of the Faeroe Channel. (From Eapp. et Proc.-Verb.; Cons. Perm. 

 Int. Explor. 2Ier, Vol. in. p. 6, Appendix G, 1905). Shews the distribution 

 of temperature. 



ridge and on either side, and shews the effect of such a barrier on 

 the flow of an ocean current. At the surface of the sea the w^ater 

 temperature is 8° C. to 11° C, and at the bottom on the top of the 

 ridge it is from 2^C. to 4°C. But it will be seen that whereas on the 

 Atlantic side the temperature at a depth of 450 m. is 8° C, on the 

 Norw^egian side at a corresponding depth the temperature is 0° C. 

 At this place we have a double flow of water : at times cold water 

 from the Norwegian Sea tends to pass over the ridge from the 

 north, while Atlantic water at a much higher temperature is 

 continually passing over it from the south. But only those layers 



