2018年6月大学英语六级听力常考时文：Obtaining Fresh Water from Icebergs

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　　1.What did scientists warn about fresh water? It will be run out of faster
than ..
        　　2.What's the difference between icebergs and sea ice? Icebergs are formed
entirely ...
        　　3.What is mysterious about the movement of icebergs? Sometimes they move in
a direction ...
        　　4.What is one of technical matters in making use of icebergs? Preventing
their ...
        　　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. 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.