新東方優美背誦短文50篇 Unit44:Obtaining Fresh water from icebergs

44.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 than smaller pieces of ice, icebergs have been known to drift as far north as 35 degrees south of the equator in the Atlantic Ocean. To corral them 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 the icebergs lost half of their volume in towing, the water they could provide would be far cheaper than that produced by desalinization, or removing salt from water.

從冰山中獲取淡水把冰山拖到世界上人口稠密的地區和干旱地帶，再從中獲取淡水，這個想法曾一度被認
為是一個笑話，更適合于卡通畫，而非現實生活。然而現在，許多國家正相當認真地考慮這件事情，特別是在科學家們發出警告之后。
科學家們認為人類將在耗盡糧食之前首先耗盡淡水資源。冰川是一個直到最近以前一直被忽視的可能的淡水源。全球四分之三的淡水還鎖在冰川的冰塊中。
冰川就是一個蓄水池，其中未開發的淡水量是如此巨大，足夠支持全世界的江河1000年。每年有7，659萬億公噸冰漂流在海洋中。
它們包含在10，000座從極地冰帽中斷裂出來的冰山中。這些冰山的90%以上來自南極。一年四季里，覆蓋
在淺層大陸架上的巨大冰川生成了眾多冰山。冰山和海水的冰不同，后者是海水自身結冰形成的，而冰山則完全是在陸地上形成的。
當冰川伸展到海水中時，冰山就斷裂下來。當漂離極地地區時，冰山有時會在底層洋流的推動下頗為神秘地逆風移動。由于冰山比小塊
的冰融化要慢，因此有的冰山在大西洋中向北飄到了赤道以南35°的地方。把冰山蓄攔起來并拖到世界上需要它們的地方將不會太困難。
有困難的是其它的技術事宜。比如，如何防止冰山在較暖的氣候中迅速融化以及如何把大量的淡水收集到岸上去。但是，即便在拖
的過程中冰山失去了一半體積，這樣做也遠比從海水中脫鹽取得淡水便宜。