陳蕙雅思教材 - 雅思閱讀精選 (Obtaining Fresh Water from Icebergs)

Obtaining   Fresh  Water   from Icebergs

The concept of obtainingfresh water from icebergs that are towed to

populated areas and aridregions of the world    was once treatedas a joke

more appropriate tocartoons than real life. But now it is being

considered quite      seriously by  many nations, especially since scientists

have warned that thehuman 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 worldfor

1,000 years. Floating onthe oceans every year are 7,659 trillion       metric

tons of ice encased in10,000 icebergs that break away from the polar ice

caps, more than ninetypercent of them from Antarctica.

Huge glaciers thatstretch over the shallow continental shelf give birth to

icebergs throughout theyear. Icebergs    are not like sea ice,which is

formed when the seaitself freezes, rather, they are formed entirely on

land,   breaking off when glaciers spread over thesea. As they drift away

from the polar region,icebergs sometimes move          mysteriouslyin a direction

opposite to the wind,pulled by subsurface currents. Because they melt more

slowly than smallerpieces of ice, icebergs have been known to drift as far

north as 35 degrees southof the equator in the  Atlantic Ocean. Tocorral

them and steer them toparts 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 wouldbe far

cheaper than thatproduced by desalinization, or removing salt          fromwater.

從冰山中獲取淡水 把冰山拖到世界上人口稠密的地區和乾旱地帶，再從中獲取淡水，這個想法曾一度被認

為是一個笑話，更適合於卡通畫，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後。  

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，足夠支援 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。  一年四季裡，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，後者是海水自身結冰 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。  由於冰山比小塊

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 來並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。