RIVERS IN THE SEA — SMITH ' 433 



would take for deep bottom water at any given place to reach the sur- 

 face. If the time .is great enough, much of the radioactivity might be 

 lost, otherwise it would become a hazard. 



GIANT EDDIES 



The major currents of the world, with some exceptions, run as part 

 of a continuous circulation, completing a clockwise circuit in the 

 northern oceans and a counterclockwise one in the southern oceans. In 

 general, the current flowing toward the Pole on the western side of 

 the ocean tends to be comparatively narrow and fast, whereas the cor- 

 responding current on the east, flowing toward the Equator, tends to 

 be wide and slow. Thus the Gulf Stream, a flow of between 25 and 50 

 million tons of water per second, is concentrated into a fairly narrow 

 stream in its most westerly part, and has a maximum velocity of over 

 six knots at times. Having crossed the Atlantic Ocean, the stream 

 veers south again, off the coast of Africa, to complete the circuit. 

 Here, as the Canaries Current, its flow is very slow and is spread over 

 a wide area. The counterpart of the Gulf Stream in the North Pacific 

 is the Japanese Current, the Kuroshio, and in the Indian Ocean there 

 is the strong Agulhas stream flowing south, off the coast of east 

 Africa. 



There are, of course, many other currents besides those which form 

 the major circulations of each ocean. Some are tidal, others due to 

 seasonal winds, to unequal heating of the water, or indirectly caused 

 by winds which pile the water up against the coast, thereby bringing 

 about a longshore current parallel to the coastline. And here it may 

 be said that, as a rule, the currents caused by winds do not flow in the 

 direction of the wind, but at an angle to it, w.ith a right-hand twist in 

 the Northern Hemisphere, left-hand in the Southern Hemisphere. 

 Thus the trade wind of the southern North Atlantic blows from the 

 northeast in a southwesterly direction toward the Equator but the 

 north equatorial current which it drives across the Atlantic moves to 

 the right of the wind, in a westerly direction toward the Windward 

 Islands. 



Although, for the most part, the ocean circulations of the two hemis- 

 pheres do not directly intermingle, there is a current which branches 

 off from the South Equatorial Current, flows across the Equator and 

 joins the westerly movement into the Caribbean. This transports 

 something like six million tons of water a second across the Equator. 

 There is no compensating surface current in the opposite direction, 

 and the North Atlantic and Polar Sea have no other outlet. Ob- 

 viously there must be an accounting for this net gain of surface water 

 by the North Atlantic, and equally obviously there must be a compen- 

 sating return movement somewhere. Since it does not take place at 



