. . . ice sheets and glaciers like those on Greenland are changing provide an indirect measure of sea-level changes and indicate trends in world climate . . . . major glaciers have sped up since the turn of the century, with documented thinning from 65 to nearly 100 feet per year.It has been estimated that a 9-inch change in the average height of the central Greenland ice sheet would result in a .12-inch change in the sea level of the world's oceans.