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 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 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.
四六级听力成功要素速度素质记忆理解
名师指导6月英语四级备考真题为先
四六级考试写作提高如何改写范文
英语六级听力考试题型应试要点解读
英语四级听力技巧掌握高频词积累惯用语
英语四六级网考未有大幅增加
四六级写作主谓不一致原因在哪里
大学英语四级简答题的解题方法
英语四六级备考阅读能力提高问答
英语学习的基本点晚输入早输出
英语四级考试阅读理解解题关键
四六级完型冲刺考前提分必知的三大技巧
教你怎样提高英语听力水平
不得不知的提高发音正确的方法
四六级听力过关半年学习计划
12月英语四级听力简评及对六级考试的提示
6月份英语四六级写作常见问题答疑
如何冶好英语四六级瘸腿的考生
四六级考试9月备考词汇记忆有讲究
教你如何征服英语四六级考试翻译失分点
英语六级备考帮你提高阅读的速度
四六级阅读备考两大法宝做真题找技巧
从心理角度提高四六级听力成绩
20分钟搞定新概念背诵
大学生英语四六级考试听力如何提高
英语四六级考试复习与心态调整
英语四级考试阅读理解必会方法
英语四六级作文如何写出高分句式
六级考试听力选择题答题方法
跟老师学英语阅读
不限 |
英语教案 |
英语课件 |
英语试题 |
不限 |
不限 |
上册 |
下册 |
不限 |