The Greenland Ice Sheet is the second largest ice body in the world, after the Antarctic ice sheet. It is about 1,500 miles long, nearly 900 miles across at its widest point, and averages more than a mile in thickness. It has experienced record melting in recent years and is a source of great concern as the climate continues to warm. The Greenland Ice Sheet is losing an estimated 270 billion tons of ice each year. If the entire sheet were to melt, global sea levels would rise by 24 feet which, of course, would be a world-wide catastrophe.