Joe Hutson, age 12, of St  Ann„ Mo 

What is an ocean current?

The Gulf Stream is an ocean current known since the earliest sailing vessels braved the stormy Atlantic  Its warm, indigo‑blue waters sweep eastward above the equator and swirl around the edges of the North Atlantic in a great eddy  This steady current, like a river flowing through the ocean, is more than half a mile deep and in some places 50 miles wide, Similar ocean currents swirl around the South Atlantic, the North  and South Pacific and the southern Indian Ocean 

Until a few years ago, most people thought that these sweeping surface streams were the only currents in the ocean, The experts knew that the deep ocean waters of the abyss did not remain still, for water is a liquid and liquids tend to mix to even up their temperature and their dissolved chemicals  The cool water in the depths tends to well up and mix with the warmer surface water, the cold waters of the polar regions mix and merge with the warm waters of the tropics  The fresh water from the rivers mixes and blends with the salty waters of the ocean,

The scientists of the International Geophysical Year studied this mixing and merging of ocean waters with new ideas and new instruments  They studied the well‑charted surface currents and they probed far below into the deep waters of the abyss  There they found other currents, counter currents running in the opposite directions from the swirling streams near the surface,

Some scientists had suspected that these deeply buried rivers must exist in the ocean.  Special instruments for probing the temperature and density  of deep water were invented and put to work in the likely places, So far, only a few places have been probed and a thorough job calls for a charting of the oceans of the entire globe, For the vast oceans play a big part in our lives in the weather and our food supplies  The more we know about them, the better 

One of the places probed was off Cape Hatteras where the Gulf Stream lashes close to the shore  Here the great surface current is 40 miles wide and 3,000 feet deep  Its warm blue waters, sweeping up from the south at about 40 miles a day, could fill the mighty Mississippi 1,000 times  Surely such a tremendous current is enough to explain the shifting waters of the North Atlantic  But not at all 

Special floats were sunk at various levels below the Gulf Stream off Cape Hatteras  At 6,000 feet below the surface of the ocean,, half a mile below the warm Gulf Stream, they found a cold countercurrent 75 miles wide, Its dense, cold waters were heading south from the polar seas to mingle with the light warm waters of the tropics  A similar countercurrent was discovered below the eddying surface currents of the Pacific, In some places, this great underwater river is 200 miles wide and it is estimated to travel a distance of 7,000 miles 

In the past, most experts thought the surface ocean currents were created by the prevailing wind belts  Now it is believed that the surface currents and the deep currents beneath are caused partly by the tendency of warm and cool, light and dense, water to mix and mangle and partly by the rotating earth which tends to pile up more water along the western side of the oceans