28 : The Atlantic 



ence the life of the ocean and also how far-reaching and yet how deli- 

 cate are the adjustments of the sea. 



Between these islands there is a ridge on the bottom of the sea 

 named the Wyville Thompson Ridge in honor of one of the early 

 English oceanographers. The ridge lies 1,500 feet below the surface 

 and over it the warm waters of the Gulf Stream pour into the cold 

 Norwegian Sea. Of course at the surface temperatures are about the 

 same on either side of the ridge, but below the ridge there is a warm 

 side and a cold side. Studies show that though they are separated 

 by a very short distance and though the same water flows freely over 

 them, the creatures living on one side of the ridge are almost com- 

 pletely different from those living on the other side. Only 11 per cent 

 of all the species counted are found on both sides of the ridge. 



It was also over this ridge in 1929 that Helland-Hansen found the 

 Atlantic water entering the Norwegian Sea to be warmer, saltier and 

 somewhat greater in volume. He thought about this and then an- 

 nounced that this should have far-reaching effects. He predicted 

 that two years after his observation the effects should be felt as far 

 away as the Barents Sea. Sure enough two years later, 1931, the seas 

 around Spitsbergen were free of ice for an area twice as large as 

 usual. Also fishing boats off Spitsbergen caught codfish in successful 

 commercial quantities, which had not happened before in over half 

 a century. 



The Wyville Thompson Ridge is part of a line that extends from 

 Iceland to the Faeroes, from the Faeroes to Shetland and then to Scot- 

 land. South and west of this the main Atlantic begins. Here in the 

 great Atlantic basin a remarkable structure has in recent years 

 emerged with new clarity — this is the Mid-Atlantic Ridge. This runs 

 in an irregular line midway between the continents, dividing the At- 

 lantic into two vast long valleys — an eastern valley and a western val- 

 ley. The ridge rises to varying depths below the surface of the sea but 

 it extends in an almost unbroken fashion from Iceland in the north 

 to the island of Tristan da Cunha in the south. Indeed, many but 

 not all of the Atlantic islands are simply the loftiest summits of this 

 vast submerged mountain chain. Such peaks are Iceland, the Azores, 

 St. Paul's Rocks, Ascension, St. Helena, Tristan da Cunha. 



Between the island peaks the ridge is submerged to an average 

 depth of 9,000 feet below the surface of the sea but it would still be 

 an impressive mountain range if viewed from the valley of the sea 

 itself. Between St. Paul's Rocks and Ascension there is a considerable 

 break in the chain like a mountain pass. 



