OCEANOGRAPHY 



415 



the isotherm for 10° C. went down to 500 metres, it here lies at a 

 depth of between 50 and 25 metres. In the comparatively short 

 distance between the two sections, the whole volume of water has 

 been cooled between 1° and 2° C. This represents a great quantity 

 of warmth, and it is chiefly given off to the air, which is thus 

 warmed over a great area. Water contains more than 3,000 times 

 as much warmth as the same volume of air at the same tempera- 

 ture. For example, if 1 cubic metre of water is cooled 1°, and the 

 whole quantity of warmth thus taken from the water is given 



22 23 - 



Fig. 4. — Temperature and Salinity in the "Fram's" Northern 



Section, Jult, 1910. 



to the air, it is sufficient to warm more than 3,000 cubic metres of 

 air 1°, when subjected to the pressure of one atmosphere. In 

 other words, if the surface water of a region of the sea is cooled 1° 

 to a depth of 1 metre, the quantity of warmth thus taken from the 

 sea is sufficient to warm the air of the same region 1° up to 

 a height of much more than 3,000 metres, since at high altitudes 

 the air is subjected to less pressure, and consequently a cubic metre 

 there contains less air than at the sea-level. But it is not a depth 

 of 1 metre of the Gulf Stream that has been cooled 1° between 

 these two sections; it is a depth of about 500 metres or more, and 



