If the salinity of ocean waters is analyzed, it is found to vary only slightly from place to place. Nevertheless, some of these small changes are important. There are three basic processes that cause a change in oceanic salinity. One of these is the subtraction of water from the ocean by means of evaporation —— conversion of liquid water to water vapor. In this manner, the salinity is increased, since the salts stay behind. If this is carried to the extreme, of course, white crystals of salt would be left behind.
The opposite of evaporation is precipitation, such as rain, by which water is added to the ocean. Here the ocean is being diluted so that the salinity is decreased. This may occur in areas of high rainfall or in coastal regions where rivers flow into the ocean. Thus salinity may be increased by the subtraction of water by evaporation, or decreased by the addition of fresh water by precipitation or runoff.
Normally, in tropical regions where the sun is very strong, the ocean salinity is somewhat higher than it is in other parts of the world where there is not as much evaporation. Similarly, in coastal regions where rivers dilute the sea, salinity is somewhat lower than in other oceanic areas.
A third process by which salinity may be altered is associated with the formation and melting of sea ice. When seawater is frozen, the dissolved materials are left behind. In this manner, seawater directly beneath freshly formed sea ice has a higher salinity than it did before the ice appeared. Of course, when this ice melts, it will tend to decrease the salinity of the surrounding water.
In the Weddell Sea, off Antarctica, the densest water in the oceans is formed as a result of this freezing process, which increases the salinity of cold water. This heavy water sinks and is found in the deeper portions of the oceans of the world.
l. What does the passage mainly discuss?
(A) The elements of salt
(B) The bodies of water of the world
(C) The many forms of ocean life
(D) The salinity of ocean water
2. The word "this" in line 5 refers to
(A) ocean
(B) evaporation
(C) salinity
(D) crystals
3. According to the passage, the ocean generally has more salt in
(A) coastal areas
(B) tropical areas
(C) rainy areas
(D) turbulent areas
4. All of the following are processes that decrease salinity EXCEPT
(A) evaporation
(B) precipitation
(C) runoff
(D) melting
5. Which of the following statements about the salinity of a body water can best be
inferred from the passage?
(A) The temperature of the water is the most important factor.
(B) The speed with which water moves is directly related to the amount of salt.
(C) Ocean salinity has little effect on sea life.
(D) Various factors combine to cause variations in the salt content of water.
6. The word "altered" in line 16 is closest in meaning to
(A) determined
(B) changed
(C) accumulated
(D) needed
7. The world "it" in line 18 refers to
(A) sea ice
(B) salinity
(C) seawater
(D) manner
8. Why does the author mention the Weddell Sea?
(A) To show that this body of water has salinity variations
(B) To compare Antarctic waters with Arctic waters
(C) To give an example of increased salinity due to freezing
(D) To point out the location of deep waters
9. Which of the following is NOT a result of the formation of ocean ice?
(A) The salt remains in the water.
(B) The surrounding water sinks.
(C) Water salinity decreases.
(D) The water becomes denser.
10. What can be inferred about the water near the bottom of oceans?
(A) It is relatively warm.
(B) Its salinity is relatively high.
(C) It does not move.
(D) It evaporates quickly.
附录：文章翻译如下
如果我们分析海水的盐度，会发现地区间只有轻微的变化，然而有些小的变化是重要的。
导致海洋的盐度变化的基本过程有三个，其中之一是通过蒸发的方式即把液态水转化为水蒸气来减少海洋中的水分。 这样由于盐留了下来，所以盐度增大。当然，如果这种方式走向极端，将会余下白色的盐晶体。与蒸发相反的是降水，如降雨，由此水被加入海中，海水被稀释，从而盐度降低。这种情形会发生在大量降雨的地区，或江河入海岸处。 因此，盐度通过蒸发减少水分而上升或通过降水或径流增加淡水成分而下降。
一般来说，在阳光很强烈的热带地区，海水的盐度略高于世界上其它没有热带那样多的蒸发的地区。 同理，在江河稀释海水的海岸地带，海水盐度略低于其它海区。
第三个可以变更盐度的过程与海洋 中冰的形成和融化有关。 海水冻结时，溶于其中的物质被留了下来。这样，在新形成的海水冰面的正下方的海水比在冰形成之前有更高的盐度。当然，当冰融化的时候，会降低周围水中的盐度。
在南极洲边缘的威德尔海中，结冰过程增加低温海水的盐度，从而形成了 浓度最大的海水。 这些大密度的海水下沉，可以在世界海洋的深水域发现。返回搜狐，查看更多