gre写作模板：Obtaining Fresh water from icebergs

GRE 写作范文5：Obtaining Fresh water from icebergs

The concept of obtaining fresh water from icebergs that are towed to populated areas and aridregions of the world was once treated as a joke more appropriate to cartoons than real life. Butnow it is being considered quite seriously by many nations, especially since scientists have warnedthat 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 ofuntapped 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 icebergsthat 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 throughoutthe year. Icebergs are not like sea ice, which is formed when the sea itself freezes, rather, they areformed entirely on land, breaking off when glaciers spread over the sea. As they drift away fromthe polar region, icebergs sometimes move mysteriously in a direction opposite to the wind, pulledby subsurface currents. Because they melt more slowly than smaller pieces of ice, icebergs havebeen known to drift as far north as 35 degrees south of the equator in the Atlantic Ocean. To corralthem and steer them to parts of the world where they are needed would not be too difficult.

The difficulty arises in other technical matters, such as the prevention of rapid melting in warmer climates and the funneling of fresh water to shore in great volume. But even if theicebergs lost half of their volume in towing, the water they could provide would be far cheaperthan that produced by desalinization, or removing salt from water.

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