『新东方在线托福阅读』为托福考生准备了ETS托福TPO/【学术文章】#13阅读练习：What does the passage mainly discuss?真题题目及答案解析，TPO/【学术文章】#13阅读原文范文音频翻译

托福TPO/【学术文章】#13阅读原文What does the passage mainly discuss?题目答案及解析-新东方托福官方网校手机版

According to the passage, the ocean generally has more salt in

All of the following are processes that decrease salinity EXCEPT

Which of the following statements about the salinity of a body of water can best be inferred from the

The word "altered" is closest in meaning to

Factors That Change Ocean Salinity 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 freshwater 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.