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    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 10，000 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.

    全文翻譯：從冰山中獲取淡水

    把冰山拖到世界上人口稠密的地區(qū)和干旱地帶，再從中獲取淡水，這個(gè)想法曾一度被認(rèn)為是一個(gè)笑話，更適合于卡通畫，而非現(xiàn)實(shí)生活。  然而現(xiàn)在，許多國家正相當(dāng)認(rèn)真地考慮 這件事情，特別是在科學(xué)家們發(fā)出警告之后。 科學(xué)家們認(rèn)為人類將在耗盡糧食之前首先耗 盡淡水資源。冰川是一個(gè)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(gè)蓄水池，其中未開發(fā)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(jié)冰 形成的，而冰山則完全是在陸地上形成的。

    當(dāng)冰川伸展到海水中時(shí)，冰山就斷裂下來。  當(dāng) 漂離極地地區(qū)時(shí)，冰山有時(shí)會在底層洋流的推動下頗為神秘地逆風(fēng)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(shù)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(yuǎn)比從海水中脫鹽取得淡水便宜。