Brian Cook, age 14, of Des Moines, Iowa, for his question:

What exactly causes the Gulf Stream?

Ocean currents are global events, governed by planetary forces with a helping hand from the  sun. The Gulf Stream is part of a vast system of surface currents that eddies endlessly in a clockwise direction around the North Atlantic. It is the largest warm current in the global ocean. And below it through deeper waters there flows a cooler, slower countercurrent in the opposite direction.

The Gulf Stream is most noticeable about 50 miles off Cape Hatteras, where its warm, blue green water sweeps northward through the cooler, greyish Atlantic. Flowing at about three miles per hour, it carried along 50 times more water than all the world's rivers empty into the sea. This is an estimated 50 million tons of streaming water per second. Its path continues clear around the Atlantic Ocean, though it changes somewhat as it goes.

Obviously, such a stupendous system of streaming water must be caused and kept going by stupendous energies. These energies include the winds, the rotating earth, and the sun, which sheds more heat on tropical oceans. The shores of the continents help to mold the Gulf Stream system into a swirling eddy.

North of the equator, the prevailing trade winds blow eastward across the Atlantic, carrying high pressure weather cells that swirl in a clockwise direction. The force and pressure of these steady winds push a mighty current of ocean water in an eastward direction across the Atlantic.

In the Northern Hemisphere, the rotation of the earth deflects moving objects to the right. Hence when the equatorial current meets the mid American land barrier it veers to the right and proceeds in a northward direction. Off Cape Hatteras, it becomes the Gulf Stream which sweeps northward to Newfoundland.

Here it spreads wider and several factors conspire to swerve it toward the east. Off the Grand Banks of Newfoundland, it collides with a strong, cold current sweeping down from the Arctic. Rotation and the coastline turn it toward the right. At this point the Gulf Stream becomes the North Atlantic Drift, a wider current that flows eastward and fingers around the shores of northern Europe.

There the main stream swerves right again and flows southward as the Canaries Current. The eddying circuit is completed when this stream makes a right turn to join the original current flowing eastward, just north of the equator.

Without a doubt, the planetary winds are the major factor causing the Gulf Stream and all the other global ocean currents. The continents cause them to curve. The rotation of the earth causes them to veer to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. This combination of global forces causes similar systems of eddying currents in all the major oceans. Those north of the equator swirl clockwise and south of the equator they swirl counterclockwise.