从冰山获取淡水 Obtaining Fresh water from icebergs The concept of obtaining fresh water from icebergs that are towed to populated areas and arid regions of the world was once treated as a jok e more appropriate to cartoons than real life. But now it is being conside red quite seriously by many nations, especially since scientists have warne d that the human race will outgrow its fresh water supply faster than it r uns out of food. Glaciers are a possible source of fresh water that has be en overlooked until recently. Three-quarters of the Earth＇s fresh water su pply is still tied up in glacial ice, a reservoir of untapped fresh water so immense that it could sustain all the rivers of the world for 1,000 years. Floating on the oceans every year are 7,659 trillion metric tons of ice e ncased in 10000 icebergs that break away from the polar ice caps, more t han ninety percent of them from Antarctica. Huge glaciers that stretch ov er the shallow continental shelf give birth to icebergs throughout the year. Icebergs are not like sea ice, which is formed when the sea itself freeze s, rather, they are formed entirely on land, breaking off when glaciers spr ead over the sea. As they drift away from the polar region, icebergs som etimes move mysteriously in a direction opposite to the wind, pulled by s ubsurface currents. Because they melt more s
