第2页 英语写作资料 精品写作素材(四) (2) 第3页 英语写作资料 精品写作素材(四) (3) 第4页 英语写作资料 精品写作素材(四) (4) 第5页 英语写作资料 精品写作素材(四) (5) 第6页 英语写作资料 精品写作素材(四) (6)
第2页 英语写作资料 精品写作素材(四) (2)
第3页 英语写作资料 精品写作素材(四) (3)
第4页 英语写作资料 精品写作素材(四) (4)
第5页 英语写作资料 精品写作素材(四) (5)
第6页 英语写作资料 精品写作素材(四) (6)
第7页 英语写作资料 精品写作素材(四) (7)
第8页 英语写作资料 精品写作素材(四) (8)
第9页 英语写作资料 精品写作素材(四) (9)
NOTE:
topaz / ’tэupжz; `topжz/ n (a) [U] transparent yellow mineral 黄玉(矿物).
(b) [C] semi-precious gem cut from this 黄玉; 黄宝石.
39 The Salinity of Ocean Waters
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 sea water is frozen, the dissolved materials are left behind. In this manner, sea water directly materials are left behind. In this manner, sea water 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.
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