CH. Il] THE OCEANOGRAPHY OF THE NORTH-WESTERN OCEAN 45 



Africa is filled with water of less density and of lower temperature. 

 From March to November the Gulf Stream area expands greatly 

 in a north-easterly direction and in the latter month has 

 approached the coasts of North Africa and Southern Europe, and 

 at the same time there has occurred an expansion of the area 

 over which tropical plankton may be found. Then from November 

 to the following March the stream regains its former volume. 

 Issuing from the Gulf of Mexico the Stream extends out into 

 the North Atlantic in a north-easterly direction but curves round 

 again to the south, forming a closed eddy of gigantic proportions. 

 In the centre of this eddy is the Sargasso Sea, a streamless region 

 filled with water of high temperature, and on the surface of this 

 float sea-weeds among which are to be found fishes and other 

 marine animals. 



In some way or other a drift or current of water takes origin 

 just north of the Gulf Stream eddy and this is the stream which 

 reaches the shores of Great Britain and Scandinavia. Towards 

 our latitudes the salinity and temperature decrease but the former 

 is not less than 35'5, and otf the western coasts of Great Britain 

 the mean annual temperature is from 10 °C. to 13° C. It is often 

 suggested that the cause of this drift is the prevalence of south- 

 westerly cyclonic storms which reach our islands, and while this is 

 no doubt a contributing cause of the movement of the water it is 

 also probable that complex thermodynamical causes are at work. 

 But however this may be it is the case that a conspicuous drift of 

 water from the subtropical Atlantic bathes the shores not only of 

 Great Britain and Scandinavia but also those of Iceland, and fills 

 up the deeper parts of the Baltic and Barentz Seas. This is the 

 European Stream. 



Now notice how the flow of this current is restricted by the 

 configuration of the ocean bed. The stream flows along the 

 deeper channels and depressions and fills up all the sea to the 

 south-west of the British Islands. It enters into the Bay of 

 Biscay and from there flows towards the English Channel and 

 through this into the North Sea. The main bulk of the stream 

 then flows to the north-east and impinges on the submarine 

 barrier which is formed by the Wyville-Thomson Ridge and by 

 the Faeroese-Icelandic banks. South-west of the British Islands 



