冰山获得淡水(obtaining fresh water from icebergs).doc

冰山获得淡水(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 joke more appropriate to cartoons than real life. but now it is being considered quite seriously by many nations, especially since scientists have warned that the human race will outgrow its fresh water supply faster than it runs out of food.
　　glaciers are a possible source of fresh water that has been overlooked until recently. three-quarters of the earth`s fresh water supply 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 encased in 10000 icebergs that break away from the polar ice caps, more than ninety percent of them from antarctica.
　　huge glaciers that stretch over the shallow continental shelf give birth to icebergs throughout the year. icebergs are not like sea ice, which is formed when the sea itself freezes, rather, they are formed entirely on land, breaking off when glaciers spread over the sea. as they drift away from the polar region, icebergs sometimes move mysteriously in a direction opposite to the wind, pulled by subsurface currents. because they melt more slowly th