Gilbert Insley, age 12, of Schenectady, New York, for his question:

Do icebergs melt in tropical seas?

Icebergs are launched from glaciers in polar regions and they melt long before ocean currents carry them as far as the tropical zone. Actually the melting process begins as soon as they leave home because the sea water is warmer than their solid ice. Their destiny is governed mainly by ocean currents, though storms often veer them off course. Icebergs carried along by cool ocean currents naturally last longer than those that get swept into warmer currents. And, of course, large ones survive longer than small ones.

In the Antarctic, enormous chunks of ice break free and a cold circling current sweeps them around and around the polar region. Penguins use them as rafts for long summer vacations. Greenland icebergs drift south with a cool current as far as Labrador. There many of them are captured by the warm Gulf Stream coming up from the tropics. It sweeps them eastward and they soon melt in the Atlantic.